a500 ?

Can you tell me what year the overdrive planetary setup pitch changed from 22.5 degree ..to 15 degree ? Also is this the same for both the A500 and the A518 ? thanks . If I go looking for an A500, might as well find the updated version.
Od gear angle changed to 15 deg. In 94 ( a 500, 90- 93 ,22 deg) ( a500, .94- up ,15 deg.) Same year break for a 518
Lon