Mint and proof sets do come sealed or unopened. I've foud them in original boxes direct and never openened from the mint!

A lot has been made of the practice of selling "sealed" or "unopened" mint and proof sets. In my time as a collector and dealer, some 45 years, I have bought and sold tens of thousands of mint and proof sets. Most, 95% or more of the time the sets are unsealed. In otherwords the glue on the envelope has never been activated, and as far as I can tell almost all modern era sets were sent out in this state.

Last week, I bought twenty sets, 5 each of 1961-64. All of these had never had the mailing package opened. The shiping tape was still intact. Upon opening the outside packages I encountered 5 sets in each package tightly sealed. Was I suprised? No. The reason why is that I have opened many original boxes to find envelopes tightly sealed. All of the sealed sets that I have ever come across in never opened original boxes were from 1970 and earlier.

I once bought a large hoard of 1958 proof sets in never opened containers. All 100 sets were tightly sealed. I have also bought unopened containers of sets which had never been sealed. And again I have purchased never opened containers which had sets in which the flap of the envelopes had a loose seal due to the infiltration of moister from high humidity levels during long periods of storage. Again the loose seal is from inadvertant moisture, a tight seal however is something which would most appropriatly be considerd an intentional sealing.

Now, to the crux of the matter! Would I pay a big premium for a sealed mint or proof set? Not unless I could get assurance that the seller had gotten the set from a never opened shipping container, and not unless I knew the seller to be trustworthy. I have enough of a gambler in me, however, that I might pay a small premium on the chance of a monster cameo, super toner or rare variety. But I buy a powerball ticket twice a week as well.