Even though I keep my eyes open most of the time, I never knew that such small envelopes were accepted in the mail a half century ago.   The smallest envelope in the image - 3 1/2 inches long by 2 5/8 inches high - was mailed in 1954 for 3 cents.  The United States Postal Service won't accept such an envelope today.  The tiny envelope is a little larger than a standard business card.  Perfect for a Valentine's Day message - don't you think!

With postage costs going up, and the lines at the post office counter getting longer, and email becoming more and more ubiquitous - when do you think the USPS will go out of business?