2005 Firm.
Of all the Colt revolver production minus the Colt SAA, in decending order of numbers is the Python, Diamondback, and Anaconda.
All three are very desirable, and if they are not prohibs, they pretty much retain alot of value.
Even the prohibs have way more value than any other prohibs. I saw the last Python that came out of the Colt factory in 2006. It was a highly engraved and gold inlayed six inch Blue Python. That was the last one.
I cannot attest to any Custom Shop parts guns that claim to be later than 2005.