I found this at a show today, never seen it before and I'm hoping someone can assist. It is a four piece body including the brass tip. The three steel portions of the body are like numbered like a test projectile. There is a brass tab on the side which is flush with the body, with with a tap it extends outward about 3mm. The top steel section rotates easily a few degrees until it hits an internal block, even with the edge of the brass. It makes no difference if the tab is in or out. The brass tip rotates with the upper steel portion and does not appear to be connected with the tab. The lower section is tight and I have not yet made additional efforts to open it. There are several inspection/proof marks, with any luck someone may recognize one or more of them. Any assistance is appreciated.
