I answered this OTOS but I'll put it up here too and with more detail/backstory...
I joined the Fenwick club in about 1978 when I scrounged up enough money to buy a brand-new FS85 at the original GI Joe's in NoPo.
It was an 8'-6" spinning rod. Still have it.
I wish I had bought the FS83C but I was a n00b and didn't know that that particular rod was headed for Hall of Fame status.
After that I would build several rods with Fenwick blanks for myself and friends.
I still have the Fenwick rod and blank catalogs around here somewhere.
FS83 = spinning
FS83C = casting
FS stands for "Fenglas" "Steelhead" (Fenglas was the blank material and Steelhead was the class of rod)
83 indicated 8'-3"
C indicated it was set up with the smaller casting guides
Some people would use the spinning rods upside down with a casting reel but you are working the rod against its spine....not recommended.
(spinning guides and casting guides are placed on opposite sides of the blank's spine)
They often get away without damage but it does look silly to me when I see it.
In the Fenglas Steelhead series of that era...
FS79
FS80
FS83
FS85
FS90
Fenwick USA ceased to exist in 1988 as it all went overseas in that year.