This is from the very compact Fostex R8 machine
Removed from a working machine, this is a good spare part to have one around, they are pretty reliable
but contain now one very obsolete chip plus the transistors/relay etc, if you have one of these reel to reels
you can keep one spare input channel just in case.
The unit can be changed by just plugging it in after unplugging the old, and good for fault finding to see if you
have a head or pcb or channel fault, removed from a working machine I no longer needed.
This board has a different chip than later models please check the revision on yours as they maybe are not compatible.
So far I have seen 3 variants of this board 2 with same number as this but different Dolby chip