These are some old Lindberg models that first came out back in the late 60's.
I built my first ones in the early 70's as a kid and spent hours pushing them around in the back yard.
A few years ago, I found these on ebay and picked them up for the nostalgia factor.
They are listed as 1/64th, but actually scale out at 1/60. These are the first of several that I modified to add in with my growing Bolt Action/Rubican collection. They are definitely NOT accurate kits or contest winners, but some stowage and replacement barrels make them great tabletop gaming models.
I've currently got three of the Centurion MK3's built and painted and am working on a platoon of MK5's with the late model 20 pdr/105mm style gun.
The IS-3's pathetic looking (droopy) plastic gun has been replaced with a 1/48 scale M3 90mm made by Aber. Again, it's not meant for IPMS, but it looks pretty good skulking around the game table looking for Tigers and Panthers to shoot.
The Centurion.... Built for a 'what if', early cold war scenario.
The IS-3 with extra bits added.