Dug the spare out and found this. Never seen a wheel like this but the tire looks original (will check date code later). Is this original and if so, what "ring" goes with it. Can't see how you would safely bolt it on and run it as-is.

 

 

All 68-77 Corvettes came with the spare mounted on a standard 15x8 rally wheel (15x7 in 68). 78-82 Corvettes came with a temporary spare, mounted on a plain steel wheel.

What year is your car? If it's a 77, there is a very slight chance that it's an OEM tire. From 73-77, the Firestone tire used on Corvettes was the "Steel Radial 500". From the day they were introduced, there were problems with the Firestone 500's. By 76, the Federal government was looking into them, and a recall was on the horizon. Firestone was still supplying 500's for the Corvette at the start of 77 production, while at the same time they were liquidating the supply of 500's they had on hand. During 77, the 500 was replaced by the "Steel Belted Radial" for OEM applications, and the Firestone 721 for retail and as the replacement tire for recalled 500's. In 1978, Firestone was forced to recall over 14 million 500's.

Starting in 78, all tire manufacturers switched to the metric sizes, that are still in use today. That tire is a GR70x15, which was last used in 77. In 78, the GR70 was replaced by the P225/70R15. Also, starting in 78, Goodyear became the sole tire supplier for the Corvette, likely because of the debacle with the Firestone 500's.

Since that tire is not a Firestone 500, and is a GR70x15, the only year it could have been installed on was a 77 Corvette.

 

that style wheel was pretty popular i think based from cragar slots. there were a bunch of wheel companies here in california making similar design wheels in the 70s.
Astro slots, or howard style. Superior made one called typhoon, fenton slotted wheels. They also made aluminum ones Ansens

 

All this would make a bit of sense. The car is a 73 coupe with 34k and 2 owners. The second owner bought it in 78 but put few miles and no upgrades during their ownership. Damn shame as the tire while has slight wear has absolutely no cracking. Time to dig up another rally wheel and "modern" tire.

 

I'm thinking it may be one of the period "wire basket" wheels as "do not use without retainer ring" is stamped on the face and the holes are not tapered for a conical lug nut.

 

There are 3 different bolt patterns on that wheel. It is original on Ford, GM, Chrysler and probably VW...