Either of the next three indicators exist, it is not harmless.shewolf51 said:The grenade itself is harmless since the pin had been bent so as to prevent it from being pulled out and the explosives have somehow been emptied out of the shell.
If the hole is in the bottom it's a training grenade, if there are holes that you can see through on the sides about equidistance apart, then it was rendered safe by an EOD tech, and if neither of these exist, you can safely unscrew the fuse/blasting cap from the top (CCW if U.S., CW if U.S.S.R.) and if you can see stuff inside or you can't wiggle something around inside (i.e. pencil) then it has not been emptied and you should turn it over to your nearest bomb squad, old explosives like that accidently kill hundreds of people a year. Someone thinks it's not real and makes it angry, something goes bad internally pissing it off.
P.S. be careful with the blasing cap on the fuze, if you aren't throwing it around it's fine just treat it like your mums best crystal, but the explosives inside that are the primary dets, and easily the most sensitive (lead stephinate, some other trace stuff). Heroes die young, legends live forever. I would also consider using some monofilament tape around the spoon before you unscrew it, you can't be too safe.