Massive chunk of steel, inheriting the ELCASET decks' transport panel and the then-new (and very large, the largest Sony will ever made, also used on the professional MX-7000 mixing board) LCD display - but the "rec-mute" button still was a side-function...
It mostly is a pity Sony didn't make a full-fledged high-end recorder with three heads and obvious mechanical upgrades from the TC-K7B.
As the "B" moniker suggests (B for "black", more like greenish bronze in reality), there must have been a silver version : TC-K8.
In fact it seems the silver version was only delivered in Canada while the rest of the world, Japan included, only saw the B version.
Apart from the meters and very marginally better specs, TC-K8B = TC-K7B.
Nudies here.