What brake booster is this?

[Gigem]

I have this leftover brake booster that I don't need anymore and want to sell.

I bought this for my 1972 GMC from LMC Truck. I have the old order, and the part number from LMC was 34-4321. See it here.

https://www.lmctruck.com/1967-72-che...-brake-booster

When it showed up at the guy's house who was helping me with the truck, he said that the booster didn't line up to the brackets on the truck. He said the bolt pattern on this booster was bigger than the bracket on the truck, if I recall. I ordered some new brackets from Jeg's, but instead of using them I found another booster somewhere else that fit the existing brackets so we ran with that.

Any idea what this booster is for? It was like $130 from LMC, and has never been used. I'd like to sell it and the Jeg's brackets, but I don't want to misrepresent the parts and mess someone else up.

Any thoughts? Thanks!