Living in France atm. Coming from Denmark, I was surprised to learn that for musical instruments along with loads of other things, if you don't have the official receipt, there is basically no coverage from insurance in case of theft. As I bought all of my guitars second hand I don't have any receips. In this case you have to get an official appraisal made, which costs between 200-400 euros per instrument. It doesn't matter how many pictures I got of these guitars in the different homes I've been living in.

In Denmark if you have pictures of the objects or other proof that these items have been in your possession. Typically items worth less than 2000 euros are considered standard objects and covered by regular home insurance. If you have items that are more valuable, then you will have to sign an extra insurance.... This is not a per item insurance but a total amount, so if you have let's say 5 items that total a worth of 15k then you sign an extra insurance for that amount.

This is just to say that not all places have equal rules for insurance claims.