Sure, if you have a comprehensive, up-to-date inventory including photos or videos, along with records of serial numbers, and professional appraisals of big-ticket items like jewelry and art -- and if your guns, jewelry, or whatever, are covered by separate riders, you'll probably have given your insurance agent copies of all that before the fact. But failing that, if you want the claim settled promptly, for the full value of your property, having receipts which include the model and serial numbers is your best protection.
The insurance company isn't just gonna take your word for it as to what was stolen...
I do not believe that my insurance company is going to believe my hand-written receipt any more than my word.
When I was 20 y/o, I had little of value and cared little if it was covered.
I'm pushing 50 now and have aquired many things. I also care for my things better than I did as a kid, and make sure that I have adequate coverage.