When doing research into prices of various old consoles and how they changed with time for the UK market most would probably look at the recently stopped Argos catalogue, and Nintendo power continues to be referenced as well, as do even older things.
However those are well known sources of information that many will have heard of, indeed for any particular field then catalogues and "trade" magazines are where most seek information on things, and are accordingly often well archived. For this thread we are after the more obscure offerings that many will not necessarily have seen and you might not have good cause to otherwise share. They can be of failed games, devices and shops or otherwise mega successful ones. Can be things stuffed in a box with a game, a flyer from a game shop, maybe a manual for a weird peripheral, junk mail for a service that failed, an advert from somewhere unexpected (remember it is parents that often buy games) or indeed just an obscure magazine (maybe even a zine). Video, audio, scan, picture you took of a contest... it really does not matter. Some background if you have it as well and it will help (or maybe help someone searching). Doesn't have to be in English either, indeed the history of games in the English and Japanese speaking worlds is reasonably well documented, though we would appreciate a translation or at least some background if it is somewhere you visited on holiday.
Some around here have been around in games for many decades but fear not if you are not so venerable; a picture of a game shop you visited 5 years ago can still showcase things some might have missed, forgotten or otherwise never known about (what is sold, size of shelves for things, any background posters/cardboard stands/... and all presumably not in a flagship shop), and in 10 years time will be another historical item. Don't worry about it being too obvious either; estimates for the NES sales in the UK are some 1.5 million, however if you have a nice copy of the paper list of example games that got stuffed in the box then by all means share here.
A house move left me devoid of most old gaming ephemera that was not games and things to play games on, and a copy of the Commodore 64 Datassette-1530 C2N manual is already online, so for to start with how about a shot of the box and manual for the unforgettable Commodore 64 classic "BMX Number Jump"