The rails were introduced somewhere between the 2nd and 3rd generation models. You will find rails in both stainless and blue. The Taurus website isn't always up to date, so trust the products you see on the shelves, not on the site. Good luck finding what you are looking for. It's not unusual to find a mixture of 2nd generation guns with and without. All of the 3rd generation models I have actually seen have rails.
I have (bought 3-3-07) a new PT145 Mill Pro and love it. It is very accurate for self-defense. I am going to carry it. I shot about 200 rounds through it a the range last weekend, with no FTF or FTEs, and I shot FMJ 230 factory ammo, 230 grain hollow point Winchster white box, and some 200 grain lead reloads. I was very happy! But, after the 200 rounds, I noticed that the rear (Heinie) sight had loosend. I notice this because I started missing the target, which I had been nailing up to then. Has anyone else had an issue with this? In trying to use the little wrench (supplied with the gun), I cannot seem to tighten (or loosen) the sight's set screw. Anybody got any comments on this? Thanks.