I can't help myself. Here's a few more of my favorite covers... The first three aren't advertising, but I thought you'd like to see them anyway.
The first cover is from the Moses Myers correspondence. His house is still standing in Norfolk, Virginia and is the oldest Jewish home in the U.S. I've provided both the front and back of the cover to show the docketing, giving the date of 1799.
This next item is the current oldest item in my collection and dates from 1790. It is from William Seton who, at about this time frame, would become the father-in-law of the first U.S. saint, Elizabeth Ann Seton. Cover is ex-Chrysler collection and ex-D. Homer Kendall. Again, both sides are shown.
The next item is a Scott 26 on cover with Scott 24 and Boston double ring hand cancel with octagonal paid across both stamps. This would have paid both the postage and the carrier rate. Neat cover, I think.
Now for some advertising favorites.
The first one hits the advertising mark on two counts. It advertises the stationers who mailed the cover and it advertises the Hudson-Fulton celebration in 1909.
The next cover used what collectors would normally think of as the reverse side (back) as the front, giving space for mailing addresses. This is evidenced by the obvious folds and the envelope flap. The Toledo Metal Wheel Company does a nice job of the address side, but the other side is spectacular.
The next cover, from the 1920s, features a logo designed by famed painter Maxfield Parrish for the Prince George Hotel.
Finally, here's a nice Express cover with all over advertising using Wells Fargo as the carrier in California.