There are lots of Beomaster 1000s!!! The 2313 is a black key model but has a separate RIAA board! I have the service manual. The 2316 had it integrated into the main board.
To connect a gramophone to the 2313 the following is note:
A stereo record player with a built in pre-amplifier such as a Beogram 1000 VFand a crystal pick up are connected by depressing the GR1 button.
A stereo player without a pre-amplifier such as a Beogram 1000 V should be plugged into the GR1 jack and is cut in by depressing the GR11 button.
No statement can be made as to what performance may be expected with low impedance pick ups of other makes.
I am sure Martin will let you know all there is to know about Beomaster 1000s - he collects them! I don't know how many variants there were, and I think Martin has said lots. If it is any indication, I have one white key service manual, two for the 2313 and one for the 2316!!