Full Idea
If a robust iron pot is attached to a bomb with a sensitive detonator. If the pot is struck, the bomb will go off, so they counterfactual 'if the pot were struck it would break' is true, but it is not a fragile pot. This is a 'mimic' of the disposition.
Gist of Idea
A robust pot attached to a sensitive bomb is not fragile, but if struck it will easily break
Source
Alexander Bird (Nature's Metaphysics [2007], 2.2.5.1)
Book Reference
Bird,Alexander: 'Nature's Metaphysics' [OUP 2007], p.29
A Reaction
A very nice example, showing that a true disposition would have to be an internal feature (a power) of the pot itself, not a mere disposition to behave. The problem is these pesky empiricists, who want to reduce it all to what is observable.