Kugelhandgranate M1913/15 Poppenberg system
Manufactured by Germany c.1915-1918 using surplus Khg M1913 fragmentation grenades.
45g explosive charge, percussive system armed by removing the pin and lifting the spoon lever on the handle, after which a sharp shock and gravity would detonate the device.
That’s what happens when you Voltron the early German ball grenade with their later 1915 stick technology. They had realized earlier with the regular M1915 percussive layout - one with a regular cylindrical head like other Stielhandgranate - you better had the heaviest head possible to make sure it landed right on its face.
Plus they were bored and they had plenty to fuck around with.