Most insurance companies insist on antiques being valued by a reputable dealer or valuer. Keep the valuation documents in a safe place and have them regularly updated to keep pace with changes in the market place.
When you ask for a valuation, it is important to say that it is for insurance purposes as the value given may be different from one made for probate or family division purposes: valuations for insurance must be appropriate for retail replacement. Charges for valuations can vary but are usually based on a time charge per day, or a percentage of value basis applied to the total value, which will decline as the value increases.The day rate basis is normally charged for time spent on site only, with research time included in the fee at no additional cost. It is normal to also charge for travel costs.
[This information comes from the LAPADA website with their permission.]