Welcome to Beoworld !
Yes, you're right, this is a Beomaster 900K in the version with flush grey front.
A version with black front, protruding from the wooden frame, also exists and both versions were
made with (900K) and without built-in speakers (900M).
Versions with built-in turntable were also available (Beomaster 900RG).
The Beomaster 900 is one of the classic B&O products.
You can find more info here:
http://www.beoworld.org/prod_details.asp?pid=378
& here
http://www.beocentral.com/families/bm900
It's always very hard to put a price tag on things like this.
Generally, it's worth what people are ready to pay and there seems to be a growing interest for the vintage things.
Condition is everything as with all other things B&O.
Martin