So this is something that I got pretty excited about when I got the sample.
This is a fantastic replica of the M1917 Eihandgrante. This was designed as both an offensive and defensive grenade and is literally the size of an egg with a fuze. The concept was that a grenadier could carry many of these because of their size.
Made of resin, these are for display, but can be used for reenacting. I would not recommend throwing these very hard, but once you buy them, they're yours to do what you want.