After many years of digging relics I have a good knowledge of the way things can change when in the ground, but even I can get very nearly caught out by making assumptions !
Had similar thing happen to me regarding making a bad i.d. on an item........ found it in a field in Normandy, covered in mud, took it to be a radio part. ( battery )..... cleaned it up and noticed the flaming grenade marking coming through the dirt. rang my contact in Lux. Police who after taking dimensions rang me back with the news that it was the casing from a US Parachute flare, the spigot had been broken off leaving what looked like the end of a long US Radio Battery..... also gave me the news that it was easy to empty....... removed and kept the parachute and got rid of the rest........
that was after 20 yrs or so, made me rethink a bit when picking up what looks like harmless stuff from the battlefields.
There have been some horror stories coming out of Belgium these last few years of people being blown to bits or severely disabled messing about with live shells and grenades......never wanted one bad enough to want to take that risk.