How can I tell which version a classic World of Darkness book is for? [duplicate]

I’m a novice in the World of Darkness games. Most of my books are purchased piece-meal through game stores. This answer has been incredibly helpful in laying out the various games and editions that exist.

I have around 30 books of various classic World of Darkness product lines – Vampire, Hunter, Werewolf, etc. However, most of the books don’t explicitly say what version of the game they are for (1st, 2nd, revised, x20, V5, etc.). This leaves me confused about which materials are appropriate for which games – and where to put them on my shelf!

How can I tell whether my books are intended for 1st, 2nd, revised, x20, or some other edition? Are there tradedress somewhere I should be observing? Or unique mechanical elements that differ?