Cathy, it could well be one of those things that was made in more than one material, e.g. my mother has an equinox vase in lustre pottery - identical in shape and size to my glass Bagley version.
The RD no. is part of the block allocated to non-textile designs according the
National Archives catalogue:
Subseries within BT 53 Non-textile Registrations
Scope and content Designs 539430-544002
Covering dates 1909 Mar. 23-June 16
Availability Open Document, Open Description, Open Immediately
Held by The National Archives, Kew
As it's not listed on Great Glass or in the Blue Book it's either a non-glass registration or it's been misfiled, which the NA says can happen. The only ways to find out for sure is either if someone could check on a visit to the NA at Kew, or to buy a copy of the details via the NA site (not a cheap option!)
TC, I'd agree with Hazel & Frank that yours is probably part of a set which would most likely have included a large bowl to sit on top of the stand, or the stand could be up-ended and used as a vase alongside the bowl.