xm211 vs m211

maybe this has been already discussed but i cannot find it, I bought an 1952 xm-211 what is the difference than an m-211 what does the X mean?

This is a guess but I think the X designation means it was produced before the M211 series was officially standardized.

Here's what I was told by the nice guy at Alfa heaven. He said the xm211 had a high nickel frame and more reinforced frame due to cracking of motor mount area in early model trucks. After this mod was proven effective they dropped the "x" and it became m211. Nice people there at Alfa heaven.