Note: My comment comes from looking up #3621489, a
movement that clearly shows at least 15j. Grade
10 is shown as 11j in both your database and the
Elgin specific one in a separate web site. I see
that all the pictures you show for this Grade 10
also show that number of jewels. The number is
not marked on the plate, it is simply seen by
observation. Each jewel seen in the plate is
really 2, one on top and one on bottom. A watch
with only 7 jewels has no visible jewels in the
plate, it's only visible ones are balance staff
pivot and cap jewel in the balance cock. 11j has
the pallet and escape wheel jewels only, seen by
their position in relation to banking pins on the
plate. Further jewels up to 17 are seen as
jewels for wheels in train, in the plate. Above
17, cap jewels are added to pallet and then escape
wheel, making 19 and then 21. Above 21, is where
you get a jeweled barrel. At least those are my
observations, so you can see this stuff when there
are no markings on the plate. My guess is either
there is a variation in jewel numbers in this
grade, or Elgin's records were in error in this
case.