If anyone collects antique (mechanical) parking meters, a friend of mine named Roger Wolf, manufactures replacement parts for the Duncan brand meters. His company is called Wolf Enterprises and also sells replacement parts for drive-in theater speakers. His website is:
http://driveinmfg.com/He bought many of the tooling, dies, and molds from Duncan when Duncan discontinued making mechanical parking meters and concentrated on making only electronic meters.
Here's a copy of the Duncan mechanical meter service guide in pdf format.