There are people here who know a lot more than I about Pythons, but yes, the earlier ones are definitely more coveted. A store around here recently advertised -- and sold -- #64 for $2750 ... without box or papers, and in about 98% shape.
As I understand it, Pythons with 3-inch barrels are also prized because they're rare; and apparently, there were some in calibers other than .357. I imagine those would be extremely collectable.
Personally, I'm a sucker for any early one with the full-checkered target stocks.
The older the better. Toomany variations to collect them all. As the illustrious Mr. Stern pointed out,the 3" is the deal. That is where I have focused my attention. It used to be the 2" but they are too easy. Good luck and say goodbye to ALL of your fun money. Hope you are single.
I am setting aside $5000 a year for gun purchases(unless something else comes up) for the next 13 years untill retirement, I am trying to find guns that will go up in value, right now mil surplus snipers and colt revolvers are on my list.