Sage S-glass rods were sold when the company was founded in 1979. The SFL factory rods were still listed on the 1982 catalog sheet reproduced in Vic Johnson's Fiberglass Fly Rods
book. By 1985 the factory rods were no longer available, but SFL rod blanks could still be had for about $30. It's been posted elsewhere on forum
that Sage serial numbers were similar to Fenwick, with the initial letter referring to the build year and 'A' = 1980 (based on emails from Sage). So Hellmtflies' rod is likely from 1981-ish.
The factory model numbers were done in a delicate white lettering on a decal with the rod parameters (first photo). The serial number is hand inked in black across the blank from the model number (second photo). The serial numbers are easy to miss. As Scott notes above, for rod blanks the model number is proceeded by a 'B' (third photo - not glass, but a very early Sage graphite blank).
The photos show the only wrap configuration I've seen on factory Sage glass. In my very biased opinion, these were the prettiest rods Sage ever sold. Aesthetically downhill ever since...