I've not put this one under 'GLASS', as feel confident it's Davidson - but famous last words and all that. Zero reaction to the u.v. torch so discounting Jobling, and having looked at Davidson's Jade on the Stewart's site - produced Jan 1931 to April 1934 only, apparently - it seems this could possibly be Pattern No. 27 - a 'boat-shaped dish' - of which 1401 examples were produced.
Unfortunately, there isn't any indication of size on the screen nor an image, so it remains unconfirmed - the piece here is 14.5/8 inches long (c. 37 cms.). Grateful please if anyone is able to confirm this one is the Davidson boat-shaped jade dish. thanks for looking.