Not sure what I was doing wrong, but couldn't get the pics to post properly...hopefully the link works.
Thought these were "interesting", as I had never seen these before. Searching the web, I found some ECHO branded scope mounts from the 50s-60s. The companies formal name was E.C. Herkner Co...hence ECHO. seems they also made some other shooting accessories so swivel studs seem like something the could have made, though I did not find a reference to such.
Just curious to know if any of the folks here remeber/have seen these...
Eddie- Thanks for the thoughts. The stock these are on was likely made in the 70-80s so that fits. Interestingly, the front stud, which has an identical profile, is not stamped like the rear. Just an interesting detail, at least to me. The echo brand, assuming that is what it means, seems to be a bit of an oddity.