The first 99,999 Pythons had no letter in the serial number.
The increase in production in 1964 indicates that the CNC machining process may have been introduced. Toward the end of 1969 the letter "E" was added as a prefix to the serial number. In 1975 the letter "E" was moved to the end of the number, becoming a suffix. In 1978 and later other letters were used.
"You made a statement that CNC machining had an impact on the possible quality or value of guns made after 1965. I have been in the CNC machining business since its introduction to the manufacturing industry. It really did not have much of an impact until the mid to late 70’s. Most machining was done on manual machines before that. One of the main reasons was the cost of the equipment and high degree of training to program and operate older CNC machines. Also they were highly unreliable. In the beginning, one needed to know a great deal about electronics just to keep them going. By 1980 they were very reliable, easy to program and produced very high quality components, much more so than a good machinist on a manual machine. So as far as quality of the parts in a Colt revolver: the ones produced on modern CNC machines were most likely superior to the older hand made versions.
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