Those are Martin style soldered toneholes.  The same-side bell keys and design of the chromatic F# key are consistent with it being based on a 1930s Imperial or Standard.  Or it could be a clone of a Martin horn produced by the Indiana Band Instrument Company.  The extensive model descriptions and pictures in the link below should give you some idea of ithe Martin that it's closest to. 

Old stencil horns generally aren't worth a whole lot, but some Martin stencils have a good reputation.  Playing condition is the biggest variable that will affect value.  Stencils tend to have less value than the cost of a good overhaul.  

http://www.themartinstory.net/version7/