Peter Dale, Ltd. in England was, I believe, the oldest specialized antique arms and armour shop in greater London and is presently managed by Robin Dale, the son of the founder. I believe the shop proper has now closed, but Mr. Dale will provide consultation and assistance as an agent for the London auctions.
Ken Drake deals in antique arms and armor of all times and cultures and occasionally will have medieval swords for sale. He may be expected to have a table at the Baltimore Antique Arms Show as well as at a few other "better" grade national and regional shows. As he lives on Long Island, he is likely to be aware of what is coming up for sale in the New York City salesrooms and he is known to undertake commission bidding for his clients at the NYC auctions. He may be contacted by mail at P.O. Box 972; Amityville, NY 11701 or by phone at (516) 799-4694.
Peter Finer is a dealer in top-end antique arms and armor and in rare arms & armor books. Besides his fabulous reference-quality full color printed catalogs, Mr. Finer exhibits at the top general antiques fairs in New York City (the International in October and the Winter Antiques Show held in January) as well as in Dallas, Palm Beach and Maastricht. His London gallery is at 38-39 Duke Street; St James's London; SW1Y 6DF.
David Petty deals in a wide range of fine antique arms and armor. I would expect that he would routinely have several medieval swords on offer (or know where to find them). He may be expected to have a table at both the Park Lane Arms Fair, the semiannual London Antique Arms Fairs and the Baltimore Antique Arms Show and has also exhibited at other of the "better" grade U.S. shows. What you want may not be on top of his table, so you should not be timid about asking, as even if he does not have any medieval swords along, he may have photographs of some that are available. He may be contacted by email at email@example.com or phone at 01628 605519 (from the US dial 011 44 1628 605519).
David Oliver, who organizes the annual Park Lane Arms Fair held in London will often know both of medieval swords on the market or likely to become available as well as who may be looking to buy such swords. He may be contacted by email at firstname.lastname@example.org, postal mail at Pennystane; Church Lane; Thropton nr. Morpeth; Northumberland NE65 7JB; UNITED KINGDOM; or by telephone at 01669 620618 (from the US dial 011 44 1669 620618.)
Most of this market is now in the domain of auctions and this is a growing trend as sellers turn to the auction model seeking the highest price for unique items; the Arms and Armour Auctions website will likely be helpful in keeping track of the auction market!