Not sure if there is a date on them or not. I can tell you that A6 compressors are available through many distributors. Old Air has them for sure. If you are looking to keep "EVERYTHING" 100% original that might be a trick !!!
Not sure about '61, but I had a '62 Cool Pack once and the compressor had a date code on it. That is one way that I proved it was a '62. The guy that sold it to me had written "64" on it.