how to I.D. a differential

[Daniel Thompson <dthompso@total.net>]

I've just purchased a very nice differential for my bugeye, looks as
good as new inside and out. No signs of wear on any mating surfaces. The
seller assures me it is a 4.22. "Why", I ask. "Because someone wrote it
in felt pen on the casing", he replies.

I believe that the only way to be sure is to count the teeth. Can
someone remind me how many there should be on a 4.22. Or is there really
a number cast into the casing or elsewhere that gives it away?

thanks,

Daniel T.