You're out and about trolling ze old boxes once again and you discover a potentially great find, but the seller wants a fairly larger sum than what most "regular" people want for tapes. Say you happen upon a good condition big box of Lunch Meat (or any older VHS release) for $30 at a swap meet. Still a decent price considering its rarity, but you understandably want to be as sure as possible. What signs could you use to identify whether the actual cassette is legit and not a duplicate merely by looking at it? Here's some tips from BoGD to help you not get ripped off.
First off, here's a common example of "prime era" T-120 cassette from 1985. The film is Vestron's release of Sudden Death from the same year with the face label gone due to age. Notice the tape flap at the top is a tan color instead of the usual black. This variation seems to have been popular exclusively in the '80s (to my knowledge), but black was used as well.
Notice the key-shaped hole in the upper center on the back panel. early cassette types, like late '70s through 1984ish, utilized the smaller hole as a plastic mold "break-off" point. Instead of a tiny screw, you'd see what looks like an soft serve ice cream "tit" from the mold injection machine. Sometimes this mold point will appear "burnt" from a VCR capstan pin crushing it. So naturally if you're scoping out a title from those years and see this "tit", chances are the tape is the genuine article.
Also on the back center right is a little oval indent stating "Made in Japan." This is another good indicator as most tapes after about the late '80s stopped filling his indent with a country of origin leaving it simply blank. You'll also see "Made in U.S.A."
That cassette doesn't feature any, but old types like those with a break-off point usually also have maker marks on the back. Examples are rubber stamping with numbers or words/numbers literally burned into the plastic. The tape flap above states "FUJI", this is another maker mark you only tend to see on old tapes. As VHS become mainstream and ho-hum, it no longer mattered to the consumer who manufactured the cassette.
The spine might yield another sign. The above pic is the left end of a cassette spine with another mark and denotation of the tape's length right above the copy tab. Again, older tapes tend to have this, sometimes "etched" into the plastic, while newer ones don't.
Remember as well, the labeling schemes video companies employed seemed to have "switched" over time. Early tapes sometimes didn't originally have a label on the front face of the tape, but had a label on the spine. "Middle-aged" tapes featured both face and spine labels. Later tapes dropped the spine label completely.
Finally, old tapes just seem to feel heavier and more solid in your hand. Modern blanks feel flimsy, lighter, and often carry a "glossier" appearance than older, duller cassettes. Also, it's good to familiarize yourself with the differences between SP and EP speed tapes. VHS releases from nearly all studios in the '80s/early '90s were predominantly recorded at SP speed and thus have more tape on their reels and feel heavier. All of these signs aren't hard set rules, more a generalization of trends, and there are always exceptions. Though I hope these will assist you in your hunting and perhaps save you from an expensive mistake.