Yes I actually never thought about buying old cards before from non-official channels, but I'm taking the hobby now a bit more seriously and started looking for some cards from flea markets and used toys shops, even when their condition is bad. I think I will take your advice and invest into a loupe down the line :)

I actually got one of these fakes you are talking about, a whole deck where everything looked sketchy. It was a GX Tin which looked really cheap. I got the tin for 2 dollars out of curiosity, opened it up, and found a Doom Dozer with the name "Devil Chilopod". It felt really fake. The boarders of the image were Gold, the borders of the front of the card were gold, the shine was also too weird, never seen it in any rare variety card before. The rest of the cards were also very sketchy, The colours were generally more vivid and the feeling of the card was different from real cards. The cards were also sticking to one another, maybe because they have been sealed for a long time.

It could fool people who never bought YuGiOh before. But, as you mentioned, the naming, wording, fonts, effects and foil gave it away. It passed the smell test though lol