Just as in their bamboo rods the early graphite rods were usually over rated for most experienced casters in terms of line weight. A rated 6wt would usually handle a 5wt better.
I have an early unsanded Orvis Performer, 9ft, rated 6wt. that I bought new in the mid to late 1970's. It definitely handles best with a 5wt. It works well with both WF and DT. In the first few years of Orvis graphite the blanks were made by Fisher.
Looks like the butt cap is marked 1181; would that be the date stamp?
Interesting re: the Fisher association with the early models. I have an older Fisher but it's glass so can't compare the blank. It's an 8-1/2 for 5 wt. On closer inspection I now see the blank is marked (not factory) J. K(or R). Fisher
8-1/2 -5 but the butt is a black plastic that says "Fenwick". Did Fisher make blanks for Fenwick? I'll have to go out to the trailer and pull out the Fenwick FF 857 (IIRC) and see how they compare.
At one time Fisher was one of, if not the largest rod manufacture in the US. They made rods that sold under many different brands. A year or two ago I met a guy at the Ellensburg FFF fly tying show who was making rods using some of the old Fisher mandrels. I've lost touch with him but his stories were interesting. He was a former tackle distributor.
I would call your local Orvis shop to get contact info for the Orvis rod shop. They can date your rod based on model and serial number. The only down side to the older rods like yours (and mine) is that it probably predates the inception of their 25 year guarantee. Although they still may be able make replacement blanks for some of their older rods it won't be under warranty. I found this out when I broke my beloved Performer a few years ago. It was not one of the models they could replace but they offered a great price on a new rod. I passed on the offer but fortunately I had a duplicate Performer that I still use on occasion.
Be extra careful about loose ferrules on older graphite. Outside of clumsiness or carelessness its one of the easiest way to break an old rod. That's how mine broke.