A real statement loudspeaker, Yamaha touted that it was "the end of the weak link"... NS stands for Natural Sound, Yamaha's top-end series, still online today, but perhaps with less stringent specs. M stands for Monitor, maturally.

Two zeros below, the 1977 NS-10M distant cousin graced many a studio throughout the 1980s and 1990s, with lots of us tweaking 'em to death to bring this tiny thingy to the limit. I still use my (tweaked) 10M daily.

The stars of the 1000M show are obviously the Beryllium domes, built with a process not so distant from the one used for the V-FET transistors from... Yamaha (and Sony).
Vapor deposited in vacuum on a pre-shaped copper mold, Beryllium is way better than aluminum, titanium, magnesium or whatever-um.
Not to mention soft domes. Yamaha's ultimate (literally) G-F1 and Sony's excellent Bio-Cellulose was yet to come but that is another story.

The NS-1000 is the "home" version, adorned with a lavish ebony/polyurethane finish and no a veneer add-on, mind you but real solid thick wood! Apart from this 8kg surplus of good looks and the protecion on the woofer of the "M", both versions are identical.

The 1000M saw an upgraded NS-2000 version (carbon charged woofer, 1982), a later NS-1000x (1984) and an ultimate version in the NSX-10000, produced in even smaller quantities for Yamaha's 1987 Centennial anniversary.
More recently, JM Lab, french manufacturer of such grand designs as the Utopia, brought Beryllium center stage again for a line of professional monitoring loudspeakers.

Unlike most audio masterpieces, there are thousands and thousands and thousands of NS-1000s around the world so catching a pair isn't difficult at all. Spare beryllium domes still are available, too, and all of these were and still are matched pairs - either you make one of the best loudspeakers ever or you don't.

A review is available here