Great thread.
I have two mtb's atm, one I'm riding now and the other in progress. Funny thing is they are both almost the exact same geometry (one is about 2" longer) but made of completely different material and weight.
The first was a freebie and is an 1987 era Raleigh Quicksilver LE, of which there is almost nothing about on the net. Obviously inspired by the
Quicksilver movie (but those bikes were roadies). It is Al and heavy at almost 32lb's but solid like a tank. It's undergone a few changes, most notably the rear gearing (Mega Range), friction shifters to replace seized twisters and bars, which I swapped out for first trekking bars and now a set of sort of bullhorn type.
The second is a 1992 steel Marin Pine Mountain that cost $55 and weighs about 20lb's with better components. It will inherit the trekking bars and probably the Brooks saddle and I may try some bike packing bags along with panniers. Otherwise it is just a strip down, repaint and rebuild project that I hope to ride in the spring of this year and across Western Canada in the fall.