Absolutely right.
I have mentioned the collector car "numbers matching" craze I witnessed some years back. Some of the people doing re-stamps would
screw up by grinding the old off, then trying to mimic the look of sand casting which is almost impossible to do. Then on top of it they
would re-stamp "too perfectly" making it worse.
These numbers and letters were stamped by a production worker or machinist, standing in a line doing this time after time all day long.
The worked didnt care about perfection, these were just stampings to identify parts during assembly. Nobody back then thought it
would matter in the least to the value of a part 60 years down the road.
Real numbers were stamped by a person that didnt care and probably had less than 3 minutes to do it in. Some letters may be upside down, some may not have been struck square, or possibly not hard enough the first swing. Those would have been re-struck, and if they were not exactly one on top of the other- who cared as long as they could be read. If the 3/16 stamp wore out, a 1/4 inch stamp would still do. Some stations may have had a "period", some might not have. The day shift guy might have used the period, but the second shift guy might have skipped it.
The ones to watch out for are the polished cases (all sand casting marks removed from entire case or worse just were stamps go) and perfect stamps that dont match the actual working environment of the day.
Lee