Agreed, especially in the '60's through '71 but then have a '72 19-3 and '83 M57 that have it on the frame; and a 11-83 M19-5 that has it in the yoke cut. I'd say it's the proof house but they're all Ulm...and the '83 57 has "IC" instead of '83' and the 19-5 has "11 83" instead of just the year.