As we know from our bumblings around shows, boot sales and fairs etc., anything in matt (

) black is scarce - although the shiny (jet) black is not. I almost never see matt black now - I don't know whether it was a Davidson speciality (in the U.K. I mean), or made by others.
Will look out for you but you could be in for a long wait. Somewhere buried in the shed there is a matt black trio - 1910M I think - shown on page 92, but am certain the frog isn't 4.5" Personally, I like the satinized/satinated black - always makes me think of art deco and the 1930/40's.
Was it produced by acid or sandblasting, or something entirely different. I know the W/Fs collectors use the word cogwheel for a similar but more pronounced decorative effect on the rims of some feet from that factory.
I don't know why the effect should be so noticeably strong and week on my two pieces - a mould defect quite possibly.