If I may make some suggestions. Be aware that you may be able to extend your household Insurance to cover musical instruments on an "all risks" basis away from the home but there may also be restrictions if you earn money from using them. Some Insurers treat them as tools of trade and could therefore exclude them - read the small print. As for provenance, if you have no proof of purchase, ask if there is another way that they would accept value/proof of ownership-such as obtaining a valuation. Make a note of all serial numbers. The Musicians Union do a good scheme too as far as I recall but if you are not already a member then it may not be so cost effective.
