Welcome to the forum Stephen

You will not find this stamp in your SG catalogue because it is a Canadian revenue war tax stamp.
It is listed in the special catalogue for Canadian Revenue stamps titled "The Canadian Revenue Stamp Catalgue" by Van Dam. This stamp is #FWT8 and has a CV of $2.00 mint and 25 cents used in the current 2009 edition.
Hope this helps
Chimo
Bujutsu