I have a 16 size NOS Star Watch Case that has a half moon shaped cut out on the rear rim.. Wasn't there some kind of Elgin 16 size that needed this to fit the case....

John Pavlik

yes John,
the 571 BWRaymond movements require a cut at about the 10 o'clock position (when looking with the pendant up and looking from the rear of the case)
this is to access the micro regulator

it is possible this was a 'universal' case also.. if it is late enough... does it have dual lever slots?

Yes Terry, it has 2 lever slots..That is what I would suspect, .... Thanks much...