Hi Anne,
I have six of these jelly moulds and noticed they had a registration number, so when I was at the London Archives checking on my hyacinth vases I looked up these jelly moulds as well. Just for fun really, I do not collect jelly moulds!
So this is what I found:
Registration number 699915
Registration date August 9th 1923
Description, A glass mould simply for packing food products
Archive Books BT 53/96 and BT 52/1014 (I have pictures of both)
There was no mention of an owner but with all the above, a keen researcher might be able to get hold of that as well.
Patricia