There are several factors that you need to consider on this question.
Do you have a standard homeowner's policy?
How much do you have at risk? Would your knives would value out @ $10,000 or would they be closer to $2500. Most HO policies cover personal collections but many states have a dollar limit on the coverage provided for collections. HO policy language varies from state to state.
Another question is business vs. personal. Most HO policies are very limited on coverage provided for business property, and some states HO policies do not cover it (business property) at all. If you have a table at a knife show with knives for sale, is that a business? It may fit the definition. In Texas where I live, the standard homeowner's B policy does not limit coverage on collections but there is a limit dollar wise on business property and as I recall, it is only covered on the home premises and then for a rather small amount.
Now, the question of covered perils comes up. For personal property (as opposed to real property) the standard HO policy covers only those perils named in the policy. The named perils are usually fire, lightning, riot, explosion, etc, including theft. There is usually a deductible applicable on an occurance basis and most companies have gone to larger deductibles that may amount to several thousand dollars. That pretty well eliminates small losses of a single or even several knives depending on the amount of value involved.
Many companies offer an endorsement that provides additional amounts of coverage on an "all risk of physical loss" basis. This eliminates the question of named perils, per above. For example, it would provide coverage for an item merely lost, when theft was not provable.
As you can see, this can be a real can of worms that has been opened. The best option is likely to have an insurance agent whom you can trust. Try to find one that is more than a salesman. Sit down with him or her and describe your circumstances. Ask what is available. Ask what the limitations on any given policy might be. The agent may well try to sell you a "floater" policy to supplement your HO coverage and in my opinion this can be the best solution. That policy will usually elimimate the question of business vs personal. Almost all of those policies provide the desirable "all risk" coverage and various deductibles are available. Keep in mind that the premium will be higher on lower deductible options.
If you have a Scagel or such that is worth thousands, you may need to schedule that item or those items for a specific amount. That will involve written appraisals and additional premium.
Finally
, keep records! Keep receipts, keep eBay documents, keep anything that will substantiate the existence of the knife and what the cost might have been. Take photos and if all this is on the computer, back it up. I have a collections program that I bought several years ago and I back it up to a thumb drive. I am not much of a computer whiz but that seems to work for me.
