I know that this is an airplane drop bomb, I just don't know the model. Hand for scale. I know it is a prototype so not that accurate.
Where was it found, even a continent might help. (From another post of yours it looks like you are from Portugal so it's likely a European or US bomb, correct?) Any idea of the nation of origin? Looking at the dimensions listed here: 50lb, 120lb, 250lb, 500lb General Purpose Bombs It could be in the 50lb class. Doesn't look llike a German SC50 to me. My first thought is that it looks like a mortar round. *** edit for *** Most US and German bombs I found images for are more cylindrical than this one. Some British bombs seem to be of approximately this shape though.
Oh no, I'm from Brazil, it was made here. And it was already told to us that it is an airplane bomb by the army.