I was hoping he would include U.S. Plate Blocks ,U.S. FDC's ,everything U.N.,Vatican City , Great Britain MNH sets and other great investments .
The best stamp investment was buying hundreds of bulk lots back in the 1980's and 1990's ,all these end of a auction lots were being given away at less than 1/2 cent per stamps ,why the auction houses would even fill your SUV for you just to get rid of the stuff.
Then
ebay came along. Everything got sold for 6 cents to 10 cent each if mounted on stock cards. You couldn't scan and list the stuff fast enough.....everything went out the door so fast you just gave up writing anything up ....scan and put a price on it .Then the return was 12X to 20X purchase price not bad for cleaning out closets of stamps .