I have never seen a 2.5-inch Python with target stocks that will letter. Target stocks are not listed as an option for the 2.5-inch Python in the catalogs. I think people like the feel of target stocks for shooting, hence I speculate that shooters commonly put them on the one model that did not come standard with them. There is also the factor that a Python should have "Python" stocks (the target stocks found on all other models) on it.
Probley on used guns they are add on`s and the originals get lost through the years. I myself done the same once with a beautiful 1950 s&w target. The gun still looks new, I have moved twice and have spent countless hours looking for those orginal smaller magnas. In fact whats worse, I pretty much started collecting in the 1960s. Back then I even bought brand new guns from gunshops and didnt even bother asking for the boxs! I wasnt alone, it was a usual thing more often than not! I have probley well over a dozzen or so almost mint old collector grade smiths and colts with no boxs!
I do not know if Colt issued 2 1/2" Pythons with Target Stocks, but like so many Python mysteries, I am interested to see where this thread goes.
Like others, I would assume these Target Stocked Pythons with 2 1/2" barrels were set-up aftermarket for one reason or another. However, about 2 years ago, the Fugates had several NIB Pythons listed on their website, one of which was a 2 1/2" with Target Stocks and one was a 4" with Service Stocks. Each were pristine, NIB examples with perfect and complete paperwork and packaging. John Fugate took the time to list these unusually stocked Pythons with detailed photos, which I have attached here (thanks John!). While, I do not think there is a way to prove the case, one way or the other, I believe these two Colts were factory equipped as they are shown here. The key for me is the upper side-plate screw head; rounded for the Service Stocks and flat for the Target Stocks. I just can't come up with a good reason for the previous owner(s) to change-out the stocks and side-plate screws and then maintain the guns in pristine NIB condition. Would the owner go to the unnecessary trouble of replacing the round head side-plate screw with a flat head, when it is completely obscured by the left Target Stock panel? I wish I had saved photos of the box labels, as I vaguely remember there being some kind of notation regarding the stocks.
As for the ones we are seeing so much of on the auction sites, my default would be to assume aftermarket modification unless there is an original box label with supporting notations, and the appropriate side-plate screw.
First is the 2 1/2" with Target Stocks: