Not sure if anyone is still looking for the identity of Pearly, but there are some identity marks that place her as an APC that is no longer used by the US Army.
Examples to compare between Pearly and an M75, is the wheel/bogey setup, the upper exhaust port (which the show attempted to disguise), the vents on the right and left side of the vehicle and the door on the front right side of the vehicle. The cupolas on Pearly also match the locations found on the upper hull of the M75. There are a few other identifying marks as well, but they were harder to match.
What would be neat, is to know where Pearly is right now, is it in a museum, being used for other movies and shows, or is she in a scrap heap somewhere waiting to be re-used.