Is the aperture sight on the block correct for a Lyman? I saw a picture of one and it was different. The base of the sight I saw was slotted for elevation adjustment.
There were two versions, early and the ones that came with the M20/1926. I don't have my safe accessible, and I can't remember which side the adjustment knobs need to be on to be "early" or "late". I'm pretty sure knobs migrated to the more logical right side, so that would be "early" and appropriate. If I was to bid that much on a rifle like that, I would find out (remember) for sure, and use it as a way to see if the sight was period-correct. Of course, with a matter of only a few years difference, we are splittin' some mighty fine hairs.