Reference Library
Pocket Watch Mainspring Part Numbers, Sizes, & Types
The mainspring provides power to the mechanics of the watch. When a mainspring breaks or no longer offers enough energy for precise timekeeping, a replacement will be required. Measure the dimensions of the old mainspring using a micrometer, and use the chart below to find proper replacement for any American movement. Note: Using proper tools for mainspring installation is highly advised.
| Manufacturer | Movement Size | Part Number | Alt. Part Number | Length (in) | Width (mm) | Thickness [Strength] (mm) | End | Purchase on eBay |
|---|---|---|---|---|---|---|---|---|
| Elgin | 18 | 812 | 21.5 | 2.90 | 0.22 |  Double Brace and Hole |
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| Elgin | 18 | 812 | 21.5 | 2.90 | 0.23 | Double Brace and Hole |
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| Elgin | 16 | 817 | 21.5 | 2.65 | 0.185 | Double Brace and Hole |
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| Elgin | 16 | 817 | 21.5 | 2.65 | 0.20 | Double Brace and Hole |
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| Elgin | 16 | 817 | 21.5 | 2.65 | 0.205 | Double Brace and Hole |
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| Elgin | 16 | 6164 | 24 | 2.90 | 0.19 | Double Brace and Hole |
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| Elgin | 12 | 2339 | 6093 | 20 | 2.00 | 0.19 | Double Brace and Hole |
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| Elgin | 12 | 2874 | 20.25 | 1.60 | 0.185 | Double Brace and Hole |
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| Elgin | 6 | 824 | 17.5 | 1.90 | 0.18 | Double Brace and Hole |
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| Elgin | 0 | 2097 | 6095 | 16.5 | 1.70 | 0.14 | Double Brace and Hole |
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| Elgin | 3/0 | 2097 | 6095 | 16.5 | 1.70 | 0.14 | Double Brace and Hole |
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| Elgin | 4/0 | 4789 | 6096 | 15 | 1.90 | 0.11 | Double Brace and Hole |
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| Elgin | 5/0 | 2890 | 6098 | 11.5 | 1.25 | 0.115 | Double Brace and Hole |
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| Elgin | 6/0 | 2890 | 6098 | 11.5 | 1.25 | 0.115 | Double Brace and Hole |
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| Elgin | 8/0 | 5219 | 6002 | 12 | 1.65 | 0.10 | Double Brace and Hole |
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| Elgin | 10/0 | 1957 | 6009 | 9.75 | 1.25 | 0.12 | Double Brace and Hole |
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| Elgin | 15/0 | 5550 | 6003 | 12 | 1.27 | 0.10 | Double Brace and Hole |
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| Elgin | 19/0 | 6330 | 11.75 | 1.53 | 0.0725 | Double Brace and Hole |
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| Elgin | 20/0 | 5015 | 6100 | 8.5 | 1.15 | 0.09 | Double Brace and Hole |
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| Elgin | 21/0 | 5327 | 6004 | 9.25 | 1.27 | 0.09 | Double Brace and Hole |
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| Elgin | 21/0 | 6246 | 9.5 | 1.53 | 0.0725 | Double Brace and Hole |
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| Hamilton | 18 | 15 | 718013 | 21.25 | 2.85 | 0.205 |  T-End |
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| Hamilton | 16 | 534B | 718050 | 23.5 | 0.30 | 0.155 | Double Brace and Hole |
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| Hamilton | 16 | 318 | 718043 | 21.25 | 2.85 | 0.2 | T-End |
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| Hamilton | 16 | 317 | 718042 | 21.25 | 2.85 | 0.19 | T-End |
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| Hamilton | 16 | 317 | 718041 | 21.25 | 2.85 | 0.18 | T-End |
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| Hamilton | 16 | 534 | 718047 | 20.75 | 2.85 | 16 | Double Brace and Hole |
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| Hamilton | 12 | 1228 | 718071 | 21.25 | 1.70 | 0.18 | Double Brace and Hole |
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| Hamilton | 12 | 3028 | 21.25 | 1.70 | 0.18 | Double Brace and Hole |
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| Hamilton | 6/0 | 1721 | 718200 | 11.25 | 1.35 | 0.135 |  T-Brace |
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| Hamilton | 6/0 | 1921 | 11.25 | 1.35 | 0.135 | T-Brace |
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| Hamilton | 6/0 | 2321 | 718201 | 11.5 | 1.35 | 0.12 | T-End |
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| Hamilton | 6/0 | 2521 | 718202 | 11.5 | 1.35 | 0.12 | T-End |
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| Hamilton | 6/0 | 2621 | 718203 | 11 | 1.35 | 0.12 | T-Brace |
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| Hamilton | 8/0 | 7221 | 718272 | 13.5 | 1.40 | 0.095 | T-Brace |
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| Hamilton | 8/0 | 7221 | 718271 | 13.5 | 1.40 | 0.085 | T-Brace |
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| Hampden | 18 | 1696 | 21.75 | 2.90 | 0.21 | T-End |
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| Hampden | 18 | 1696 | 21.75 | 2.90 | 0.23 | T-End |
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| Hampden | 16 | 2696 | 21.75 | 2.90 | 0.19 | T-End |
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| Hampden | 16 | 3696 | 21.5 | 2.70 | 0.2 | T-End |
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| Hampden | 16 | 3696 | 21 | 2.70 | 0.19 | T-End |
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| Hampden | 16 | 4697 | 21 | 2.70 | 0.18 | T-Brace |
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| Hampden | 16 | 5697 | 21.5 | 2.70 | 0.165 |  Hole |
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| Hampden | 12 | 6696 | 18.5 | 1.80 | 0.18 | T-End |
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| Hampden | 12 | 12696 | 19 | 1.40 | 0.175 | T-End |
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| Hampden | 6 | 8696 | 16.25 | 1.75 | 0.165 | T-End |
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| Hampden | 3/0 | 9696 | 13 | 1.40 | 0.16 | T-End |
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| Hampden | 8/0 | 15696 | 8.25 | 1.25 | 0.14 | T-End |
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| Howard | 18 | 55 | 23.5 | 2.80 | 0.205 | Hole |
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| Howard | 16 | 328 | 21.5 | 2.75 | 0.165 | Hole |
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| Howard | 16 | 329 | 21 | 2.70 | 0.18 | T-End |
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| Howard | 12 | 552 | 19.5 | 1.80 | 0.15 | Hole |
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| Howard | 12 | 553 | 19 | 1.80 | 0.16 | T-End |
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| Howard | 10 | 796 | 16 | 1.50 | 0.15 |  Hook |
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| Illinois | 18 | 47302 | 53 | 21.5 | 2.90 | 0.21 | T-End |
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| Illinois | 18 | 47303 | 21.5 | 2.90 | 0.22 | T-End |
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| Illinois | 16 | 47309 | 27 | 3.00 | 0.155 | Double Brace and Hole |
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| Illinois | 16 | 47315 | 20.5 | 2.70 | 0.185 | T-Brace |
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| Illinois | 16 | 47317 | 573 | 20.5 | 2.70 | 0.21 | T-Brace |
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| Illinois | 16 | 47321 | 1770 | 22.5 | 2.70 | 0.18 | T-Brace |
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| Illinois | 16 | 47326 | 22.5 | 2.70 | 0.175 |  Motor Barrel Brace |
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| Illinois | 16 | 47327 | 22.5 | 2.70 | 0.175 | Motor Barrel Brace |
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| Illinois | 16 | 47331 | 22.5 | 2.70 | 0.175 | Double Brace and Hole |
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| Illinois | 16 | 47333 | 124 | 20.5 | 2.90 | 0.2 | T-End |
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| Illinois | 16 | 47334 | 20 | 2.50 | 0.21 | T-End |
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| Illinois | 13 | 47337 | 1845 | 18.5 | 1.35 | 0.18 | Motor Barrel Brace |
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| Illinois | 12XT | 47337 | 1845 | 18.5 | 1.35 | 0.18 | Motor Barrel Brace |
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| Illinois | 12 | 47343 | 18.5 | 2.00 | 0.17 | T-Brace |
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| Illinois | 12 | 47344 | 1236 | 18.5 | 2.00 | 0.18 | T-Brace |
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| Illinois | 0 | 47358 | 981 | 13 | 1.70 | 0.13 | T-End |
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| Illinois | 3/0 | 47358 | 981 | 13 | 1.70 | 0.13 | T-End |
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| Illinois | 6/0 | 47364 | 1422 | 10.5 | 1.20 | 0.13 | T-Brace |
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| Illinois | 6/0 | 47371 | 12.5 | 1.40 | 0.11 | T-Brace |
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| Illinois | 18/0 | 47383 | 10.5 | 1.20 | 0.09 | T-Brace |
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| New York Standard | 18 | 2190 | 20 | 2.90 | 0.23 | T-End |
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| New York Standard | 16 | 3349 | 20.5 | 2.45 | 0.22 | T-End |
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| New York Standard | 16 | 3196 | 20.5 | 2.45 | 0.22 | T-End |
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| New York Standard | 12 | 4284 | 18 | 1.83 | 0.2 | T-End |
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| New York Standard | 12 | 4144 | 19 | 1.90 | 0.22 | T-End |
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| New York Standard | 10 | 7080 | 17 | 1.50 | 0.19 |  Tongue |
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| Rockford | 18 | 644 | 22 | 2.90 | 0.22 | T-End |
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| Rockford | 16 | 822 | 20.5 | 2.70 | 0.205 | T-End |
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| Rockford | 12 | 932 | 18.75 | 2.00 | 0.172 | T-End |
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| Rockford | 0 | 1077 | 13.75 | 1.70 | 0.14 | T-End |
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| South Bend | 18 | 19528 | 21.5 | 2.95 | 0.195 | T-End |
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| South Bend | 16 | 17528 | 20.5 | 2.55 | 0.2 | T-End |
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| South Bend | 16 | 27528 | 21.75 | 2.80 | 0.19 | T-End |
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| South Bend | 12 | 55528 | 19 | 1.98 | 0.175 | T-End |
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| Seth Thomas | 18 | 536 | 141 | 21.5 | 3.30 | 0.19 | T-Brace |
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| Seth Thomas | 18 | 729 | 141 | 30 | 3.30 | 0.22 | T-Brace |
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| Waltham | 18 | 2203 | 21 | 2.90 | 0.225 | T-End |
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| Waltham | 18 | 2203 | 21 | 2.90 | 0.22 | T-End |
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| Waltham | 18 | 2203 | 21 | 2.90 | 0.215 | T-End |
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| Waltham | 18 | 2222 | 25 | 3.30 | 0.16 | Hole |
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| Waltham | 18 | 2205 | 21 | 3.00 | 0.22 | T-End |
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| Waltham | 16 | 2208 | 21 | 2.30 | 0.22 | T-End |
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| Waltham | 16 | 2227 | 2267 | 25 | 2.80 | 0.18 | Hole |
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| Waltham | 16 | 2218 | 2267 | 25 | 2.80 | 0.19 | Hole |
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| Waltham | 16 | 2247 | 2268 | 19.5 | 2.60 | 0.17 | Double Brace and Hole |
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| Waltham | 14 | 2234 | 19 | 1.30 | 0.175 | Hole |
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| Waltham | 10 | 2234 | 19 | 1.30 | 0.175 | Hole |
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| Waltham | 14 | 2252 | 2269 | 19 | 1.62 | 0.17 | Hole |
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| Waltham | 12 | 2224A | 2279 | 19.25 | 2.15 | 0.16 | Hole |
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| Waltham | 12 | 2224A | 2279 | 19.5 | 2.15 | 0.15 | Hole |
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| Waltham | 12 | 2224A | 2279 | 19.5 | 2.15 | 0.14 | Hole |
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| Waltham | 6 | 2215 | 16 | 1.90 | 0.21 | T-End |
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| Waltham | 6 | 2217 | 16 | 1.90 | 0.19 | T-End |
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| Waltham | 6 | 2219 | 16 | 2.10 | 0.15 | Hole |
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| Waltham | 0 | 2220 | 16 | 1.50 | 0.15 | Hole |
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| Waltham | 0 | 2228 | 15 | 1.70 | 0.13 | Hole |
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| Waltham | 0 | 2230 | 2278 | 15 | 2.05 | 0.14 | Hole |
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| Waltham | 0 | 2230 | 2278 | 15 | 2.05 | 0.13 | Hole |
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| Waltham | 6/0 | 2226 | 2276 | 13.5 | 1.50 | 0.12 | Hole |
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| Waltham | 6/0 | 2235 | 13.5 | 1.30 | 0.13 | Hole |
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| Waltham | 6/0 | 2226 | 9.5 | 1.50 | 0.12 | Hole |
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| Waltham | 12 | 2237 | 2269 | 19.25 | 1.70 | 0.165 | Hole |
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| Waltham | 7.25L | 2238 | 2274 | 12 | 1.30 | 0.11 | Hole |
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| Waltham | 6.5L | 2239 | 2272 | 9.75 | 1.05 | 0.1 | Hole |
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| Waltham | 4L | 2240 | 2260 | 8 | 1.10 | 0.09 | Hole |
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| Waltham | 7.5L | 2250 | 11.25 | 1.15 | 0.11 | Double Brace and Hole |
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| Waltham | 8.75L | 2242 | 8.5 | 1.40 | 0.085 | Hole |
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| Waltham | 7.5L | 2234 | 2266 | 13 | 1.12 | 0.1 | Hole |
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| Waltham | 6.75L | 2244 | 2261 | 7.75 | 1.20 | 0.065 | Hole |
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| Waltham | 16 | 2246 | 17 | 1.50 | 0.165 |  Double Brace and T |
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| Waltham | 6/0 | 2248 | 2265 | 12 | 1.50 | 0.1 | Double Brace and Hole |
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| Waltham | 6/0 | 2248 | 2265 | 12 | 1.50 | 0.11 | Double Brace and Hole |
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| Waltham | 6.75L | 2249 | 2263 | 7.5 | 1.15 | 0.065 | Tongue |
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| Waltham | 7L | 2249 | 2263 | 7.5 | 1.15 | 0.065 | Tongue |
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| Waltham | 6.75L | 2251 | 2262 | 9.5 | 1.30 | 0.08 | Double Brace and Hole |
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| Waltham | 7L | 2251 | 2262 | 9.5 | 1.30 | 0.08 | Double Brace and Hole |
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| Waltham | 8.75L | 2253 | 9 | 1.30 | 0.085 | Double Brace and Hole |
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| Waltham | 8L | 2253 | 9 | 1.30 | 0.085 | Double Brace and Hole |
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| Waltham | 37 | 2232 | 2280 | 28.25 | 4.50 | 0.23 | Hole |
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| Waltham | 37 | 2232 | 2280 | 28.25 | 4.50 | 0.22 | Hole |
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| Waltham | 22 | 2245 | 2275 | 25 | 5.40 | 0.22 | Double Brace and T |
Data Source: BestFit Mainspring Chart