This is a "fire grenade"

"We found several of these old fire grenades in the attic of a large, old house in Edina [a suburb of Minneapolis, Minnesota]. It's a glass bulb filled with carbon tetrachloride, and was supposed to be thrown at the base of a fire to help put it out.
They were withdrawn in the 1950s because the chemical is toxic, and heat from fires can apparently turn the chemical into phosgene gas. Found among the Fun home inspection photos from 2016.