Hi guys, here asking for some advice.

A few years ago I picked up six bootleg Bowie albums from a charity shop and I'm hoping someone can help me identify/value them?

I have six all from different shows throughout the 70s and 80s and no way of telling if they are originals. (Although I only have three to hand hence the pic.) All are in plain cardboard sleeves with pasted on paper posters and are on either blank discs or ones that are labelled as other artists. Some sleeves have two vinyls in and some are just single disc. All are in excellent condition and the sound quality varies as they are mostly live recordings with some rare studio stuff as well. The three pictured were recorded in the US between 72 and 76 and the UK between 68 and 84.

I'd be grateful for anyone who can help me figure out where they came from and if they have any value as they are obviously not on discogs due to regs about selling bootlegs.

Thanks!