Originally Posted by
clubman
Probably the gray 7 speed shifters, below XT. If I get it, you'll get the serial number, thx.
I went back and checked the 1990 catalogue and there were no models with thumb shifters, so they do appear to be a modification by a previous owner. Also, there was no Nova Pro model in the 1990 catalogue or the 1991-1992 price lists, though in 1992 there was a Nova with Exage. So, it's still looking to be no earlier than 1993.