If it is a yellow label with Stereotape or The Reel Society printed on the label with a dot matrix printer, these are legit. It is possible that the tape is not original and the original reel and box were re-used.
Here is the history...
Stereotape started selling tapes directly and through a limited number of distributors in the mid-70s. However, given that duping open reels is a labor intense proposition unlike pressing CDs, they tried a number of approaches to reduce their costs. These included using previous boxes and graphics with 3 3/4ips listed when the tape was really dup'ed at 7 1/2. And the use of computer printed labels prior to the cheap laser labels of today. In the era, the labels were printed on a continuous feed dot matrix printer.
You will even find 7 1/2 ips tapes from Stereotape where the box and the reel label say 3 3/4ips. All they did was put a 7 1/2ips on the shrink wrapped box.
Let me know if you have other questions on Stereotape, Ampex, or B-C reel tapes.
the real question is how did they sound?