Sorry I have been slow on this. As you suspected it is a Deserter GT built by a collaboration between Dearborn Automotive and Autodynamics the largest race car builder in the US at the time. They were built in Marblehead, MA, which makes them fairly rare on the West coast, but far more common on the East coast. They have a 84' wheelbase as opposed to 80" for most other shortened buggies. It was done that way for somewhat better street handling than the Manx and clones.
Dearborn also made the S1 model which looks more like the Manx, but is also 84" wheelbase.
Production numbers that are usually quoted are:
S1 bodies = 802
GT bodies = 410
GS (mid engine kit with either S1 or GT body) = 138
There is a loosely formed "club" of Deserter Owners with a useful web site
http://www.deserterownersgroup.org/
There is also a Yahoo group
https://groups.yahoo.com/neo/groups/des ... group/info
Dearborn Auto Inc still exists and restores and trades vintage cars. Alex Dearborn owns one of the nicest Deserter GT's you will find, and his son a very nice GS. He also has a web site with a history link to some first hand history of the development of the cars and the ideas behind them.
http://dearbornauto.com/
http://dearbornauto.com/deserter/index.shtml
All are useful. There Bob Elliott and a few others have done a great job of keeping track of the history and somewhat of a registry of owners. Deserters have some very unique history. One ran the 24 hours of Daytona, and several at Pikes Peak Hillclimbs. One became an SCCA Solo II National Champion. There are a couple of suppliers of new parts for them, as well as a wealth of useful information (the windshield is from a Renault Dauphine, and they are available). The top you have is very nice. It is one of a few tops available with the Deserter kits. There is even someone producing new Deserter kits, but I don't know anyone who has bought one. Dave Barrett at manxchassis.com has one and produces some special chassis improvements for the Deserter S1, GT and GS.
Like a Manx, some Deserters came with ID plates that seem to be mounted at random places inside the body. It was an option so all do not have the plates (extra $3 in the purchase
Yours looks like a great find. Get in touch on the Deserter people. They have more information about your buggy.
Calvin