manville singel shot

ok this was passed to me, I am told it was my grandfathers gun, it is a single shot, 12 guage gun made by Manville manufacturing company, the gun works like a syringe , you place the end of it in your paml and using your middle and index fingers you pull the tigger back to fire the gun, the barrel about 5 inches long unscrews off the gun, im thinking its a 1 shot tear gas gun, anybody have any info or pics on this gun? worth? rare? its not for sale just want info ,

hello where can I get the information on year, made, type, etc on this Thompson auto ordincae sub machine gun serial number 218974 please

ok well maybe someone can help me, i have a weapon, teargas gun ,other? this is a 12 guage chamber, the barrel is i think about 4-5 inches long it unscrews fron the gun , the gun is held in your palm like a syringe you pull back on the two levers and it fired the shell, the only name on it says manville manufactoring company, so that led me to think of gas gun, i have only seen one other one in a crime labs display case,