Beautiful snake. I have one much like it but (I'm sorry to say) not in quite as nice condition.
I have a 1964 4" Nickel and the underlug is hollow. I've always been under the impression that the underlug became solid in 1965.The hollow lugs were a feature of the early Pythons. In the past on this forum there was much discussion on when that feature was discontinued.
The likes of your gun will never been seen again. Do you know how to pre-index the cylinder when closing it to avoid a turn line? Hold back the cylinder latch and 'locate' the cylinder so that the bolt only contacts the cylinder notch leads as the cylinder is closed. Rotate the cylinder in a clockwise direction after closing.
A properly timed Colt will never exhibit a cylinder turn ring if it is always pre-indexed upon closing. No other American made DA can claim this.
Sometimes one needs to travel the path under his own power before understanding the journey. If he sells it, as it appears he will, he'll soon realize the folly of his ways, or not. I've a '78 I picked up a few years ago that came with Colt pachmyers and the cylinder face had been a little too aggressively buffed by the previous owner so it shows a hint of copper around one cylinder chamberI think is OP is making a BIG MISTAKE SELLING THIS SNAKE. It is rare enough in this configuration but it is a gun you will never be able to replace in this condition and you will have setller's regret JMHO.....Mike
I know somebody who has one for sale. Pm meI've been looking for a 4" nickel for a long time---and still looking----you be very lucky. Should you ever decide to part--give me a shot!
Thanks!