because I can't really find information on this set or what it's worth (if anything).
The folder was seemingly not what you were asking about.
Kenmore is a large company that has been selling stamps and coins for many years. The folder is just a fancy package since they obviously came into a large number of these stamps, enough to justify creating these folders. Nice, but I doubt anyone would pay much of anything for just the folder today over the selling price of the stamps. You can be sure that the original buyer paid for the cost of that folder, too.
This is a very specific and limited package and unless someone happened to buy one whenever it was being sold AND remembered the details, I doubt anyone here could give you more info. for there are many, many other packages like this in the stamp and coin worlds where we don't have any details like date of release. If you want a history of the folder, Kenmore still exists and you could ask them directly:https://www.kenmorestamp.com/