There is no limit. Insure your watch for the correct value, i.e. how much it would cost to replace it new at today’s prices. To make sure you don’t under-insure your watch, take it to a jeweller for a new valuation every few years. Note that if your watch is worth less than £1,500, it doesn’t need to be individually specified on the policy, but do include the value of it in the total value of contents to be insured.