from a google search: (l999 Chicago tribune article)
The U.S. Postal Service first sought to raise the price of mailing a first-class letter nearly 18 months ago. Millions of those rooster-on-a-weather-vane stamps--formally called "the `H' rate make-up stamp"--had already been printed.
But the one-cent rate increase to 33 cents wasn't actually approved until May of last year and the decision to make it effective Jan. 10 wasn't made until June. That's a long time coming.
(You can go to google but this stamp was necessary to affix to the 32 cent because of the rate increase at that time until they could "catch up" to printing the new rate stamps)
hope this helps.
Given that long lead time, it is even more puzzling why customers had such trouble finding those elusive roosters when the new rate finally went into effect