Anne, it is Sowerby's Number 2583 - called a "Celery Vase" (that euphemistic term :wink: )
Yours is F 2583. Two other shapes (flared points up and down) were also made. Also supplied with holder and plinth.
Incidentally, our second Sowerby CD-ROM is ready (covers the 1920s through to the 1960s). It includes illustrations of this item in the original Sowerby catalogues. I'll post full details tomorrow.