In the early 70s, John W. Caler Books advertised in Air Progress magazine, and I bought some from the enterprise. The company started a book club with the promise that all who signed up would receive a piece of a Messerschmitt 109. (Bf or Me, they’re still 109s) I signed up, received a few lists of books for sale and bought a few more, including some German language reprint, reduced in size, of 109G maintenance manuals, well illustrated. They’re still in the AeroKnow collection. I was satisfied with the piece of the 109 and will someday display the card with a late-model (probably 109G from Hasegawa) 1/48 machine.
I lost touch with the Caler operation. Perhaps they folded. If you know what happened to the businesses or 109, please update in the comments.
Abe Lincoln's Air Force 
I too bought a piece of the 109, although a bit later than you did – I had membership number 349. Here’s a good summary of what went on before, during, and after the times we bought into this attempted restoration: http://www.indianamilitary.org/FreemanAAF/Aircraft%20-%20German/FE%200124Bf109G14/0124.htm
I have posted on Ebay one of the Membership Cards with the covering piece. Item #331356527201