The above object turned up on a conveyor belt at the Mr Chips potato chip factory in Auckland, New Zealand. It looks like a raw whole potato but in fact it's an old grenade. Fortunately, it was a training grenade and did not contain explosives. From RNZ.com:
It was initially thought to be an unusually shaped rock, but staff soon realised it was a grenade, prompting a call to the police who arrived quickly.
"The bomb squad then came out and did a whole assessment of the grenade, before they determined that it was infact an inert grenade, training grenade," [said factory operations manager Roland Spitaels.]
Spitaels said since the discovery they'd learnt there had been a number of army training camps held around the Matamata area, which is probably how the grenade had ended up in the field.