What’s the Best Way To Present a Large Collection to a Dealer or Buyer?

There are a lot of potential answers to this question, but more information is needed for the right answer.

Possibly the most important thing to consider is: Was the collection/accumulation formed randomly, by accumulating stamps as opportunities presented themselves, or was it formed by careful buying of quality material from dealers or auction houses?

If it was the result of careful purchasing, and you know there are items of particular value, then those should be organized to present nicely to potential buyers.

If it is really just a casual collection/accumulation, then it probably would not be worth the time spent to do a lot of organizing.

If the potential buyer is a dealer, they will be able to assess the potential resale value quite quickly (most dealers have gone through this drill dozens, or hundreds or thousands of times already - they can assess even very large collections very quickly).

If the potential buyer is a collector, they would probably prefer having the collection remain largely "unchecked". A neatly sorted collection or accumulation means that there would be little chance of finding hidden gems. (The term hidden gems is not intended to mean a rarity or high value - what it means is finding a $1 value stamp mixed in with many 5¢ stamps, or a $10 value stamp mixed in among many $1 value stamps).

Other considerations are that, while it is easier to find a potential dealer buyer (just go to a stamp show and you will find many there in one place) a dealer will be offering you a wholesale price, which is based on what their potential resale (profit) will be, combined with how long the items will remain in inventory. If they decline to make an offer, it doesn't necessarily reflect on the collection itself, but is more a reflection of what they want/need for their own inventory. (For example - don't offer a collection of modern foreign topicals to a dealer who specializes in classic US only).

Selling directly to a collector might yield a better price, but finding that one interested collector is a lot harder than finding a potential dealer buyer.

Another possibility is to take the collection to a local stamp club meeting. My own local club (in CT) runs auctions for our own members, and is a frequent buyer of collections to sell at our own auctions, or to sell at our monthly local stamp show.