This is an official letter from the Lone Scouts. Note the return address: Lone Scouts of America W. D. Boyce : Chief Totem, 500 N. Dearborn Street Chicago, Ill. USA. The envelope was used to mail the pins to a Lone Scout member, Jack Mason in St Williams Ont. Canada. These are the Lone Scout 1st Degree, 2nd Degree, and 3rd Degree Pins.
There is no date on the postmark- but the stamp is 1910-1916 era. Because Boyce ran the Lone Scouts as a business, it is likely that this envelope was mailed when the stamp was a current issue for sale at the post office.