I think I know what Benjamin was saying, but not to put words in his mouth, I will repeat the impression that it is machine doubling on the date, and that the part above the 2 might be a die chip. The reason it can't be an underlying "1" is apparent if you look at a photo of the 1942/1 P or D mercury variety. The "1" is to the very front of the 2, about at the upper serif of the "2". The spacing is different for the 1941 date due to the "1" being narrower than the "2", and the date was applied all at same time and not one number at a time.
Welcome to the forum Retired!
Jim ( also retired )