Basically a turbo off a 7.3 Ford powerstroke diesel.
Could be any number of trucks, even a bus.
They list in the $1200 range, but can be picked up used under $400.
Diesel truck turbos are not a good source for cheap turbos to put on a hot rod gas motor.
Garrett makes a ton of OEM turbos, just because it is marked Garrett does not make it aftermarket, this one sounds like an original truck turbo.