Sometime ago I was asked if a recently purchased German incendiary bomb was empty or not as the owner could not unscrew the nose fuze. After all these years a large amount of these Incendiaries wont unscrew due to the magnesium expanding with damp.
There are several ways to have a check to see if your one is possibly live.
First, when shaken, does it rattle? If it does this is usually a sign that the fuze has been removed and you have a retaining collar left inside.
Second, with a piece of flexible wire, fashion the end couple of inches into a right angle and gently insert it up inside through one of the fire holes. If there is an obstruction it still doesn't mean you have to panic, it maybe the split collar has got caught sideways inside the body.
Third, if methods one and two fail then weigh the body using suitable digital scales. These are the weights I obtained from my examples...
1 Kg standard incendiary all weights in Lbs using digital scales
Empty AZ83128* nose fuze no striker etc 1.437 Lbs
AZ8312@ nose fuze with striker etc 1.503 Lbs
Complete with empty charge case inside 1.598 lbs
1.3 Kg Steel nose fuze AZ8313 no components in fuze 2.235 Lbs
AZ8313 with components in fuze 2.303 Lbs
Remember, there maybe slight variations but only minor. Anything much heavier then caution is required.