A photograph and drawing of this particular celery is shown in Thompson, and in the book (page 49) against this item it says '(Imit. cut)', so am assuming that 268968 No. is registering the pattern only, and not the shape of the celery vase.
I've linked another recent post .....
http://www.glassmessages.com/index.php/topic,46050.msg258064.html#msg258064 - from which you can see the same mould pattern - and again seems to be just the pattern being registered, and not the shape.
The similarity to cut glass is quite strong, and this design of deep mitres - from a slight distance - certainly give the impression of cut glass - plus it seems to have an unusually good 'ding' when struck - might this contain some lead?
The date of Registration is 13th January 1896, and height is about 7.3/4" Does anyone know how many different shapes might have carried this No., aside from these two?