Last successful period for Revox, with "modern" looks (by essence a relative notion) inherited from the B225 CD player.
The B215 belongs to the moment when blank and pre-recorded cassette sales topped LP sales for the first time (1984) and before both formats would rapidly loose ground to CD.
The B215 is therefore built like a topper from a topping time with an enormous diecast aluminium chassis for the drive and four motors with dual-capstan.
The two hardened-steel capstan axles are polished to micron tolerances and the related flywheels are almost big enough to power an ELCASET drive !
That drive was inherited from the B710 MKII and also shared by the A721 Studer version of the B215 ; it was kept in later versions of the B215 : B215SG (1989) and H1 (1990).
Added to the B215 was electronica aplenty.
Three processors allow bias & eq to be set automatically, to use the B215 as multiroom source and display its status elsewhere, plus provide a number of cue / marker / programming and go to functions.
Not to mention pre-set levels, real-time level adjusting, elapsed time, fade in & out and the locate & repeat functions.
This is when it is getting a bit complicated : when simply adjusting something means using the two display areas, long sequences of key hitting and display confirmations.
A simple but very important thing : there is no red LED to confirm record mode is on - just a small grey mention of it in the grey LCD meters ! The A721 has the LED - why not the B215 ?
Most japanese makers weren't putting all this in their decks in 1984/85, except Teac and its Z-7000 : they knew DAT was coming fast and it would be much easier to implement such features onto a digital tape with ABSolute time !
Not often known but crucial : if Studer made its own heads for its open-reel recorders, the Sendust & Ferrite heads of the B215 (and those of other Revox cassette recorders) came from either Sony or Matsushita.
Many detailed images, technical descriptions and nudies here.
The drive itself can be seen with an exploded view here ; it is that of a B710 - same difference.