Not many Colts are valued at $50 these days. But to answer your question, the serial number reference listing in the book, Colt An American Legend is considered by Colt as the authoratative reference until 1985. I'm at work, so am doing this from memory. You can call Colt customer service to get a date of manufacture on any gun, but that is the only information they will provide for free. Most of us use the above book as our primary reference for dating colts by serial numbers.