If there is no registration mark I suspect it's not Burtles & Tate
A while ago, Roy, who posts here under mhgcgolfclub sent me this note:
"I was just looking through the Burtles and Tate section of your web site and you have 2 pictures of Swans, the 2nd picture of the single swan looks very very similar to me of a later swan made by the Cambridge glass company of the USA, I once bought a pair of swans which looked very much like Burtles although they were a slightly strange colour of blue very much like the one in your picture,they were not signed, just something you may like to check out"
That sounds like a pretty good description of your swan!
Incidentally the swan which Roy was referring to on my website did in fact turn out to be Burtles & Tate as the owner was able to find a reg number on it.
Some swan pictures on this page:
http://sites.google.com/site/molwebbhistory/Home/registered-designs/burtles-tate-designs-by-date/burtles-tate-1885I'll have to add a note about these off-blue swans... they do look very similar. From your photos compared to the real B&T I would say that the angle on the neck of the swan is not as acute as the real thing.