Hi,
just to add some debate to this post, have you actually thought if it is worth having insurance to cover costs of lost keys.
Our company holds key for over 50 premises, (touched wood before I typed) and have never lost a customers key yet in the 15 months we have been trading. Our customers keys are kept in a commercial lockable keybox, and was not cheap, but IMO a well worth purchase.
We insist with our customers that we only have one key to only one door. Therefore, should a key go missing, the customer would have a key to open the door. This means that you would only have to pay a locksmith to change a barrell. On checking with a local locksmith, I was informed that it would cost me approx £60 - £100 for a complete lock change.
On this basis, my company would have to lose 3-4 sets of key a year just to break even with a £400 a year insurance policy. Furthermore, when I ran this scenario by my accountant he is confident that the expense could be lost as a legitimate business expense with the tax man...
Hope this helps
Paul
Edit: typos