axle ID? (7-9/16", aka amc15)

[Tom Jennings <tomj@xxxxxxx>]

My 73 parts car has an "H" axle code (2.73:1). So it's got the
right speedo gear (luck!) I need for my 70. Maybe someday
if I get ambitious I can make a twin-grip out of it.

But there's two stamps on the boss:

H

and beside it, rotated 90 degrees, in slightly smaller letters:

YH

Does this mean anything? Never saw this before.