Seen that one a few times, never been able to id it.
Which means it's almost certainly not
Percival Vickers, Robinsons, Sowerby, Davidson
Unlikely to be Molineaux Webb or Joseph Webb
Not going to be Greener or other northeast with that density value.
Which leaves likely makers as
Burtles Tate
Edward Bolton
Ker Webb
Derbyshires
or other
Ker Webb uranium yellow density is quite specific at around 2.8g/cc
I'm not sure the method you are using is accurate enough to place it to them though. You'd need to be sure you are accurate to 1-2% and I feel some of your results are more 5-10% variance (sorry Nev!)