A view from a guy with over 45 years in the wholesale auto parts business;

The difference may be where the dist was sourced from originally. Prestolite sold parts to many wholesale auto parts suppliers and even direct to normal auto parts stores, not just through auto manufacturers. I know of mom and pop auto parts stores that have been buying direct from many such manufacturers and suppliers since the late 1940's. Years ago, I was buying Chevrolet Delco distributors, but not through the GM dealer channels. I have also bought bulk quantities of NOS Accel distributors in genuine Mopar boxes through contacts in the speed shop industry. The aftermarket and dealer parts supply system have many different branches, where many of the same parts can be bought through different channels, when the only visual difference is the packaging or maybe the tag or label on the part.

The stamped tag is likely only an indicator of through which channel the distributor was purchased.