Early Militia Artillery Box?

I was hoping someone could shed some light on exactly what I have.  Attached you will find pictures of a tin belly box or side box that I was told is early militia (1820's or earlier).  It appears to be in very good condition except for a missing divider on the inside.  I can tell there was some sort of divider from the old weld seams that are still present.  It has a hinge interlocking piece on one end and is curved to be worn on a belt on the hip or belly. 

When I received this item I was told it was shown to William Guthman of the Antiques Roadshow and he identified it as a very rare early militia Artillery box that would possibly hold fuses.  Mr. Guthman told him that it was very rare and he had only seen 1 other.  My dealer was in the process of receiving paperwork from Mr. Guthman when he passed away and had this box tucked away ever since. 

Could you possibly confirm the age and type of box if possible?  I'm interested in possibly selling it but until I know exactly what I have and its value I'm not sure where to start.