I've been watching these guys sitting forlornly gunless since their Python was stollen in a burglary over 30 years ago. I think it's time for closure but I have no idea what to ask for them. They're Gen 3s that didn't spend a lot of time on the gun.
Those are indeed Gen 3 target grips. The most valuable ones are Gen 1, which are fully checkered. Completely original (not all are), a good pair of Gen 1 will run $400 and up. Unless the market has really changed, a good pair of Gen 3 grips (which are fairly common) will normally sell for around $150. Look on eBay to see if you can find any listed.
Right now there is a pair of fairly good looking Gen 3s on EB currently priced just a little above what I earlier mentioned. You might also check to see if any are listed on GunBroker.
I have bought a few Colts just to get the target grips.
Those are the 3rd version Python stocks, the cheap ones. Worth a measly $200 for a fast sale to $300 for someone who just has to have a set. I find it fascinating that the factory wood stocks now cost almost as much as I paid for my Python revolvers many years ago.
Just like the gun itself, prices on original factory Python stocks are listed at ridiculous prices these days. I wonder how many people are actually buying them at the high prices. I would rather spend the $200-$400 on ammo, leather, or speed loaders.
There are some decent-looking repro Colt target grips available, but even they are in the $200+ price range. 30 or so years ago you could walk into some gun stores and buy a pair of Colt target grips from the junk box on the counter for $5-$10. I bought two pair that way and still have them.