I thought I remembered something I read a long time ago about a gun called "The Greener". After some searching ,this is what I found. So, I think the gun in question is probably a knock off.
A popular gun was called the Greener gun, invented and manufactured by William Greener of Birmingham, England. These guns fired large, heavy harpoons into the whale at a greater distance than was possible with a hand darted harpoon. These guns could also fire a large bomb lance into the whale. The Greener gun allowed a much heavier projectile than a shoulder gun.
