Postage due stamps are also part of the postage stamp stock the postmaster at Fossil, Oregon can use. To reduce the time and effort of canceling stamps, the same precancel device as used on regular postage stamps (see the article on Fossil, Oregon precancel stamps) was used on postage due stamps.
Fossil, Oregon Postage Due Cover
The first class surface letter rate increased from 10¢ to 13¢ on 31 December, 1975. This cover is dated 11 January, 1976 and has a manuscript marking indicating three cents is the amount of postage still due. A total of three cents in postage due stamps was applied to conform to the new rate.
The Mesozoic Times 