Maybe production numbers for black were lower than other colours, but for me black is always a very difficult colour to find. There's hardly a boot sale I visit where Davidson/Cloud glass is absent, but it's always other colours. The seller insisted this was Wedgwood 'basalt'.
Seems that this design may have started somewhere in the early '20's and may have still been around in the '40's - although believe there was a long gap in the production of black in the 1930's for some reason. Black can grow on you - very classical and stately, and pic. is just for show - understand there may not presently be the level of interest in Davidson there was a few years back - diameter is c. 6.5" (165mm).