Careful guys! I've pasted from my reply to an earlier thread last year:
I don't know much about the policies purchased through musician's unions or those type sources. However, I am an Allstate Insurance agent, and can tell you some things to be aware of when insuring your basses on a homeowners/renters policy. You should verify your own company's policy stipulations:
First, most auto policies I know of do not cover any contents, other than what was originally designed to go into the car (ie: the car stereo, but not your CD collection,power amp you installed under your seat, your bass, etc). If someone breaks into your car and steals your bass, its a homeowner/renters policy claim.
Second, our homeowner/renter's policies have additional coverages you can purchase, one for "professional" music equipment, and one for "non-professional" equipment. (Playing for pay = professional) Again, check with your own agent for additional coverages they may offer.
Thirdly, all claims are subject to whatever deductible you choose for your property policy, so don't claim a MIM Jazz Bass if you have a $500 deductible, as you won't get anything.
If you have ANYTHING remotely resembling "vintage" or "custom", by all means, have it appraised! It will make for a much fairer settlement when dealing with an adjuster who, you will do well to remember, doesn't know a bass you play from a bass you catch. Their job is to try to settle each claim quickly, but to spend as little of the company's money as possible. Have something to back you up.