round

I got this yesterday from the antique center at EX RAF Hemswell, has anyone got any idea what is is? You can see a red detonator through the hole in the end. The only markings are the stencils you can see (36\SM MK1 MOD3) no stamps that I can find. Could it be an inert practice round, USAF...

Toronto Blue Jays move into the next round after awesome but confusing Game 5. The umps call was correct on the ball hitting the batter. Had this game gone wrong, I think TO would be burning now. Geo