> We asked Bomb disposal unit from a
>nearbye army base to remove the material.

There are really two questions here.  One, and most important, is the safety
issue. The second is preserving as much of the artifact as possible.  Sadly,
the two are often at odds.  Few military or police disposal units have the
skills or the inclination or equipment to disarm (as opposed to destroy) many
types of shells. For most of us the only choices are the military or police,
who, more often than not, will chose to destroy shells, mines etc. as this is
often the least dangerous way to handle the stuff .  For the well funded
museum,  there are just a couple of folks in the USA who specialize in
disarming  this sort of thing.
     And a question, how many of you all have heard the story of
Bannermans'(sp?) Island? Bannerman was a New York based arms dealer who used
large quanities of outdated, mostly American Civil War,  shells as fill at his
island and there they remain.