Odd Stamp (pressed) on Obaks. What is this?
 

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):

Looks like someone's monogram stamp. H R L, perhaps?

I had a collection of '39 Playball cards with the exact same hole punched in them. The cousin of the cards original owner said that "Greg had them on a string so he could flip through them". They could have been made with a leather punch due to the shape but they are exactly the same as the ones i mention above.