I'm writing this both as an army reservist and a historian, and I cannot underline this enough:

If you suspect something might be an explosive, DO NOT TOUCH IT. It is NOT a plaything, nor a fun curiosity.

Even century old explosives can still have the potential to explode, and may have grown progressively more unstable over time. Leave the object alone, and contact the appropriate authorities. This will usually be the police. Let them determine how to proceed.