Just because cameras are old does not mean they all of a sudden take bad images. I think all the early cameras, not just from Pentax, take good images.
This includes, apart from the Pentax *istD, the Olympus E1 (5MP) and the Panasonic L1 (7.5MP).
These early initial models had sensors in the 5 - 7.5MP range in them which produced some amazing images. I still use these cameras extensively today.
Some more images to come from these early cameras in due course.
Note: The Sigma lens cost me some 30 Euros new !!! Not half bad stopped down to f8 or f11.