The SP was quite a long lasting rod, and a few versions autoclaved and pre-autoclave.
I had 2.75lb TC SP's with a black/dark grey reel seat, around 2005. This was a brown blank. From memory the number of the blank was printed on the butt and the tip section so I was always able to match the correct butt and tip. I don't think it is a model number, I actually think it is the number in the run.
I'm not sure when the steel reel seat came into vogue, probably around 2011, but I could be wrong