It's after market. Nice job but repop
I went back and looked at the pictures again, I still don't se anything that really stands out to indicate it cannot be factory, what are you basing your assessment on?
Here are copies of some the pictures I used for comparison, some might be after market but I can't see any feature that stands out to help definitely determine that. I know the 29's are factory, I had a discussion several years ago about the poor quality of the factory checkering on the Model 29 pump 22's, they had standard checkering from the mid 1930's at least to 1949. I also think the 110's and the EG are too, the other are questionable, what are some opinions on No 1, No 6 & No 7? Especially No 1, since that's a rifle that is listed as having checkering as an option and No 6 & No 7 are not.
The 1949 catalog still had the Model 320 & 322, 1950 was the fist with the 340 and listed the checkering option but without a picture.