In the process of cataloging a large collection, we came across this unusual pressed stamp on 3 different Obak cards. I'm curious if anyone has seen a stamp like this before? I've tried to do a Google image search by uploading a tracing of the stamp, but it didn't return any matches.
Full size scans of the cards on Flickr:
http://www.flickr.com/photos/strejc-...on/8058113680/
But it's easier to see from an angle (attached):