Likely more of interest to advertising cover specialists or bicycle history enthusiasts than revenue collectors, but I just loved the aesthetics.

Sent from one of the proprietors of Schwind & Garrabrant to himself. We know with certainty that it was philatelic due to the whimsical message on the enclosed matching letterhead:

Friend Walter

This is your Birthday so I thought I would write a few lines to myself wishing myself a happy return of the day and try to get a Revenue stamp to take it. I remain

Respectfully

W. W. Garrabrant

A lovely set of items IMO.