But seriously... It's a reference to the world cataloging of coins. I believe 90a is the Krause numver for Indian Head cents.
Sure bust my balls. My google is weak and I found what you did. I got that the KM: is Krause,but the 90A didn't register....90a the Krause number for Indian Head cents makes sence.
Thanks, I always wondered where I could get a watt-hour meter tester http://www.knoppinc.com/Specifications/Bulletin 1008 KM-90A.pdf