Counterfeit NES/SNES Games-how to know if it's fake?

As a Famicom collector with 185 games, 51 Sufami games and a handful of Famicom disk games, I have never once doubted the validity of the games I am buying- because I've never thought of it (probably because I do all my buying in person and not online). Most counterfeit games I have seen are of the multi-cart style, where you might get 40 games in one, and then it's really easy to tell they are fake.

But, for things that might be counterfeited, I can only suggest comparing what you see for sale online with images of the same game available elsewhere. Unfortunately Sufami and most NES games use a standardized cart design and color, but if you were buying Famicom games one of the giveaways would be the cart color itself. There is a thread on reddit that points out to basically compare with other images online, and get high-res images of the back of the cart as well to check on the validity- number of screws, type of screws, warning label. A big give away could just be wear-and-tear- if the game is OOB and looks perfect, that would be a red flag.

The only retro games I own where I doubt their validity are games on magnetic disc, like the aforementioned Famicom disks and older floppy disks (IE used on Commodore 64 / Amiga) as you can re-write that data pretty easily.

Just last night I received a copy of a SNES game that was a fake/reproduction that I bought off EBay.

How did I discern that?

1. Image/Look - Compare it to a real one. Sometimes this involves comparing images of a claimed real one on google or EBay.

2. Weight - The weight of the cartridge didn't feel right. I compared this to a copy of Mortal Kombat 2 I had owned for over 20 years and discovered this fake cart was 74g and the Mortal Kombat 2 cartridge was 91g. This is not always accurate as some cartridges had some different hardware in them, such as the SuperFX chip, but it was one sign that something was off.

3. Screws - The screws were the same gray plastic as the rest of the cartridge and weren't actual screws, they were merely part of the cartridge made up to look like the actual screws.

4. Label - The label didn't look properly glossy. It was curved around the edges, but there was a slight imperfection in the cutting on the lower right side and the images seemed to be "scrunched". The "Nintendo Seal of Quality" was slightly smaller than it should have been and lacked the detail you would normally expect, seemingly from a lower quality printer and or poor scan.

5. Cartridge not snapped - The cartridge (the front and rear) weren't snapped together in all parts of the cartridge, as if someone didn't finish clamping it together after it was made.

6. "New" - EBay seller, after looking at the auction again, described it as "New", when it was just the cartridge, which is not technically possible for an authentic game.

7. Manufacturer - EBay seller claims, in the details, that the manufacturer was someone I've never heard of, and not anyone associated with the original creation of the game/cartridge.

8. Item Creation Location - EBay seller claimed it was "made in China", which isn't normal for a video game, but since the fake/reproduction cartridge was made in China, that somehow fits their version of it, and demonstrates that it's not what you're looking for.

9. Electronics - If you open it up and you can see small blobs of solder on the board that don't look like they were done by a machine on an assembly line, then someone did it by hand and its not authentic. If the chips are really small (as in they look like today's chips), then its also a fake/reproduction cartridge as chips back when these old cartridges were created that were that small simply didn't exist or were too expensive to mass produce for game cartridges. Lack of "Nintendo" and such on the electronic breadboards can also be an indicator of it not being "real".

10. Conversation - If when you complain to the seller on Ebay that it's "not authentic" and they respond with "what's not real" and proceed to claim its the "same game, levels, story" and that the original carts "cost much more" , then you know its a fake/reproduction. That was literally the response I got when I complained. Notice when you say "not authentic" and the seller response with "what's not real" when you didn't even use the word "real"; they've clearly had that conversation before.

11. Rear Label - The rear of the cartridge didn't have the "warning" label on it.

12. "Nintendo" relief - On the rear of the cartridge, the SNES cartridges are supposed to have raised letters that say "Nintendo". This one had the oblong shape wherein the raised "Nintendo" was supposed to be, but it didn't have any letters in it.

13. Sometimes it may be hard to determine whether yours' is real. You may have to look for claims of "authentic" as many of the fake/reproduction cartridges I've read (particularly on EBay) don't claim they are "not authentic". It seems that "authentic" is no longer the rule on EBay, but the exception. I'm guessing this is more and more often the case on other websites as well. You may have to do your own little investigation as well. Some sellers seem to think that as long as they don't claim its "authentic" when its not, that somehow their conduct is "okay", minimizing the chances of someone claiming "authentic" when it is not, as they don't want to get themselves in trouble. Truth is, they're likely in trouble in spite of that, but that's their logic, not mine.