I've seen pictures of those. Would they be technically M26 or M26A1? And how did some Pershings end up that way?

The double pin tracks were available even in 1945. One tank so equipped was part of the "Zebra Mission" batch of 20 tanks that arrived in February, 1945, but it was knocked out almost immediately be a heavy artillery shell. The additional tanks shipped to Europe through VE Day all appear to have had the single pin track, however.

Both track types were in inventory, and the single pin and double pin tracks were used interchangeably through the Korean War. The double pin type seem to be more common on the M26A1 rebuilds, though, and fairly universal on the M46 Patton.

The M26A1 had the updated gun with bore evacuator and single chamber muzzle brake (aka blast deflector), but lacked the new drive train used on the M46.

Tracks were not related to the vehicle's designation.

Thanks. As it happens, I have a metal aftermarket "old" cannon and a set of later tracks. Unfortunately I read that both the Tamiya and Hobby boss vinyl tracks have serious seam issues. Needless to say, I'd but the kit which could accommodate both items, preferably a Hobby boss one.