This is one those things I found on the job site today. Do you know what it is? I do not.
It is a brass cylinder, approximately 1 1/4" in diameter, and 9 1/2" long. In construction, it appears to have been hand brazed. It also appears to have had a bright red label at one time. There is no opening in the unit other than the valved port you see. It is operational. It is under pressure, containing some unidentified gas. Although it was unwise to do so, I smelled it, and it smelled like alcohol.
Whatcha think?