They are from my Dad's 1988 S-10 Blazer and camr on it from Dennis Chevrolet when bought in new. The writing on wheel is 4x4 and 15x7. Or if you point me to where a serial.numer or model is.
I would pull one off and look on the back side. Most of the time wheel manufacturers will have the brand, size, and 9 times out of 10 the model number stamped onto the back of the spokes.
Considering they came on the truck new, it was most likely a dealer option, so tracking down an original center cap might prove to be pretty difficult... You may have to settle to just measuring the diameter and ordering and trying a cheap aftermarket one on it.
They look a LOT like the wheels that came on the old Dodge Ram SST Indy 500 Pace Tuck package; that's the first thing that popped in my head lol. But defitely not the same wheel, completely different lug pattern, and they were 17"s... BUT, very good possibility it's the same manufacturer...