The closest there is to the kind of resource you are seeking is Springfield Research Service, Box 126, Cabin John, Maryland 20818. They have been in business for years and have published a great deal of information about Trapdoors and Krags as well as other US military firearms. Not only have they compiled and published a wealth of information, but they have become the most knowledgable about the records available at the National Archives. If you want them to look for information about a specific U.S. military firearm, they will look through their existing records for a price. And, if you are willing to foot the bill, they will go to the Archives and look more deeply for you. There is one other source that might be applicable. In some very, very rare cases where a Trapdoor or even a Krag was given to a state to be used by the National Guard, that state's archives may hold information about that firearm. I've found a little bit about state issued Potsdam muskets and Trapdoors this way, but once again, this kind of information is very seldom available. Best of luck and keep us posted on what you learn.
