to the Family, vintage 109!
This is an example of the Postmaster General Favor First Day Covers.
James Farley sent many, many of these out to people over the course of his eight years as PMG. These are highly collectible, but not overly valuable.
A check on eBay
will get you excited as Bill Langs has a slew of these listed for between $150 and $3,000.
Don't get too excited, however. If you check "SOLD" listings, the prices range around $10.00.
Given the fact yours is a souvenir sheet, I would be a buyer at around $20-$30 for it.