Hello, I just acquired this axle here not too long ago and was wondering if anyone knows what it might be??

 

A web search of that casting number brought up a parts listing on Rock Auto for a 1959 Cadillac Fleetwood Series 60:


https://www.rockauto.com/en/catalog/...nion+seal,2380

 

Looks like Cadillac to me.
Probably 1957 or earlier, judging by the leaf spring pads.

 

look at the yoke it says 1957 and newer. The older yokes did not have that deep of a saddle for the u joint. They were very shallow saddle yokes 1956 and older. low power application.
The early yokes only had slots doe the round u joints and the straps were the only thing to hold the twisting torque...PRETTY scary...lol. Jim