[Edward Tinker]

A couple of points;
1. there is a description and pictures of SEAR Safety and Magazine Safety in the FAQ
2. That many times the word 'rework' is not true - the magazine safety was added at same time as the sear safety but then removed in the late 1930's - sometimes they were cut off, sometimes they were removed completely with the side welded in (little rectangle on the side, like yours) and the hole for the safety welded in - these I believe were reworked because of the welding and heat involved. Sometimes you find the hole just left there.
3. If reworked or re-barreled by the police, then it would show a new marking on the barrel as acceptance.

So, sometimes there is 'proof' they were reworked and sometimes they weren't marked.