Just came into possesion of 5 boxes of 20 rounds each of old German made 11mm Mauser ammunition.The outside of each carton is dated 1887 and the ammo inside is in reasonably good codition considering the age.
Would there be any collector interest in these?

There might be. A good place to find out would be:

http://cartridgecollectors.org/

Are you looking to sell it? PM me with the price if you are.