Technical ID this manual steering box?

Number on the Pitman arm looks like M T 7830838, which gave me zero in a google search. I can snap a couple more shots if it helps.

Just wondering if it's a Vega box, or junk; it looks pretty but fairly certain it needs rebuilding, it was left outside for an unknown length of time. I presume it's GM of some sort, though. Shaft is too short for late Corvair.

 

looks like a 1960s GM car manual box. But it's hard to be sure, a couple more pictures might help.

 

The number gave me a link to an aftermarket arm for 64 Chevy fullsize and 65-72 midsize GM, although it was a Summit part and no clear reason why that came up on the page. Maybe that's what it is.

 

Looks very similar to the one I took out of my 64 BelAir when I converted to ps.

 

GM 525 box