Etachron Stud Dimensions - Homemade 'wrenches'

[Simeon]

I am planning on making some homemade Etachron tools from brass rod.  This will be flattened and formed into a a flat crescent, with a slot filed into it that will act as a wrench for turning studs. Would steel be better? I could use pieces of old mainspring that I have annealed to allow them to be filed to shape.

Does anyone know the dimensions of the studs?  Are they all the same? I know that there are differences between Seiko and ETA.  I only have one watch on hand with Etachron (an ETA based movement), I can measure this but I don't know if that would do for all ETA based Etachron.

[Malocchio]

I filed a Seiko regulator wrench out of a screwdriver.