If you were looking at a stainless single action with black checkered hard rubber grips, and a 5.5" barrel, I would guess that it is a New Vaquero. It would include the internal lock and thinner grip frame.
Nope, it was truly a Blackhawk .357, had adjustable sights, and on the left side said Blackhawk. I just didn't note the length of the barrel, other than it wasn't 7-1/2 or 4-5/8. After putting the question here, I went back the next day with serial numbr history for the .357 Blackhawks as well as my tape measure, and a reminder to check on internal lock. My intent was to buy it if there was no internal lock. But, alas, it was gone. The stainless ones come with rosewood grips but this one had the black hard rubber grips.
OK, one simple question will answer this mystery. Was it a flattop or not?
Like someone already said, the stainless XR3-RED type grip frames on the regular Blackhawks do not have locks in them yet. That is why they have wood grips.
The stainless flattops (also marked the same as the regular Blackhawks) will have the stainless XR3 grip frames with locks, hence the black grips.
I really don't think there is any mystery here. You just need to be a little more observant of what you're looking at when contemplating a gun purchase.