RE: What does weathering for us....
About half the M-46s in my Battalion were converted veteran M-26s with some being reconverted M-26A1s. The Marine 1 & 2d Divs had the newer stuff, having been able to get fully equipt before deployment. Our company had 5 or 6 tanks damaged 46s returned as M-46A1s, but the Army had to piecemeal everything and there was no ideas about getting new tanks...just upgrading as we went. (The 46A1 had only internal changes with relocation of the driver's control panel moved from center behind the front plate to the right of the driver.)
Many WW II tanks also served in Korea and beyond. Even obsolete Stuarts served through the entire war and were used as armored police or border security for a short time after 45.