Another thought: If you suspect it is a militia coat from Massachusetts, contact the Massachusetts National Guard Military Museum and Archives in Worcester. They have been great people with whom to work when researching Massachusetts' WW1 veterans. If they have information, they will be glad to send a copy to you. Their service to me has been prompt (usually 1 - 2 weeks). Ask if there is a fee for their service. It has been free, but with the financial mess in the Commonwealth, they may now be charging. The complete address is given below.
The Commonwealth of Massachusetts
Massachusetts National Guard Military Museum & Archives
44 Salisbury Street
Worcester, MA 01609
To Join the Company of Military Historians click here