If you join up to the Yahoo group glassaholics, there used to be a fellow who posted there called Gary who collected swans, i.e. D&M, pierpoint, etc. Many of his swans are in the photoalbum, which at least offers you a clue to i.d.
It's a very posting heavy, social group so if you do join up don't choose to have all the postings emailed to you, or your mailbox will overflow very quickly!
Actually Anne, I've just gone through Gary's 42 photos of a million swans and nothing immediately jumped out at me as being similar to yours. You might like to post them on the group and see what they say.
All the best,