The BBC Master is basically a BBC B on steroids; it has sideways RAM built in so that you can soft load ROM images into it, which meant I could install certain "ROMs" into whatever machine I was using and have full word processing and DTP no matter which room I was in when at college (pretty handy, considering the number of rooms I got kicked out of). Note also the Electron Plus 1 style cartridge slots in the front. I'm note sure they were used much, as the BBC range was already much more advanced than the Electron and so not quite so reliant on third party upgrades, certainly not ones that plugged in to cartridge slots anyway.
This particular machine I bought for £20 from a car boot sale. The guy was going into his sales pitch, I was standing there nodding dumbly like I didn't know what a computer was, and I got him down from £25 because "that's all I have in my pocket". I'd actually drawn £40 out of the cash machine just in case. He thought he was getting a good deal because he knew he was talking bollocks when he spoke of all the software available for it - yeah, plenty of software, but a regular punter would have to go back in time a decade or so to find it in the shops. I knew I was getting a good deal for those sweet, sweet dual 40/80 double sided floppy drives - my BBC B only has a dodgy 40 track drive with no case, which won't handle all those floppies I manually converted from single to double-sided using a steel ruler and a Stanley knife then reformatted to 80 tracks. The casing to the drives is metal, more than strong enough to handle the monitor I've added to the setup since they're in a convenient side-by-side configuration rather than the up-down style I was used to at school/college.
Maybe the guy at the car boot got the last laugh - the keyboard's a bit shagged so I can't play Elite on it properly, and I specifically bought a "new" version of BBC disc Elite to get the Master version (second hand for a fiver at a Wakefield show). This is apparently a common problem, so beware; at least I have other machines I can use instead. There's also rumours of early models having problems with exploding batteries bursting their way out of the top of the case like a bad Alien parody.
BBC Master Compact
An upgrade to the BBC Master series which I couldn't really see the point in at the time of release - I think it cost about the same as a regular BBC Master but had the incompatible 3.5'' ADFS floppy drive. This disc type and the keyboard being separate from the base unit, plus the early stab at a desktop system on the Welcome disc, speaks to me of an early indication of the way things would go with the Archimedes A300 and 400 series.
This pretty sweet setup - complete with monitor - I got off the newsgroups for a reasonable price, although I can't remember what. My usual price is about £30, so this case can't be far off. I had thought that it wasn't going to turn up, but it was just the previous owner trying to find me a backup of the welcome disk which was well worth having.