Hire an expert appraiser to do a thorough picture/text appraisal of each piece, then submit to your insurance agent and request an additional rider on your policy.
My ins. agent told me my homeowner's would suffice, but they just don't get the prices of these pieces. When I began to break it down to him, exact prices I mean, he coughed and said an additional rider on my policy would be suggested.
For pre-owned bags, etc., find an antiques or estate appraiser if you can't find an Hermes expert and provide them with pics, text, and some "proof of prices" (websites, those Japanese booklets are a start, receipts if applicable, etc.). After they look at the collection they'll put together a detailed appraisal. Submit it to your ins. agent, request the additional rider, then you're covered. The appraisers suggest doing it regularly (as prices increase, since recovery is at current prices).
HTH