Below is the footnote from the UPSS Postal Card Catalog (2010 edition):
"N.B. At the time this and also S14 were in use, the Post Office Dept.warned that they had been "heavily" counterfeited. However, counterfeit
copies are extremely rare. Counterfeits are sometimes coated on one or both sides to give the impression that previous printing had been covered.
The arrest of Louis Smith in 1902, who also coated genuine cards as a legitimate business, ended the distribution of counterfeits. While the
generally poor quality of genuine copies of these cards makes counterfeits difficult to detect, all cards so far positively identified as counterfeits lack the bottom serifs of the second "T" in "STATES."
"One known group of counterfeits also contains an attested counterfeit of S15 in unused condition. It is mainly identifiable by the extremely poor quality of the paper. One postally used copy of this S15 counterfeit is also known to the Editorial Board (See Postal Stationery: Jul 1957, pg 8, Sep-Oct 1969, pg 314-315, Sep-Oct 1971, pg 128-132, and American Philatelist, Vol. 98, No. 2, issue dated February, 1984, for an article by
Frank B. Stratton. Also, see Postal Stationery: Nov-Dec 2002, pg 157-159; May-Jun 2002, pg 58-60; Nov-Dec 2001, pg 104-109; and May-Jun 1989,pg 73-78"
If Don's illustration is a postally used example of the counterfeit, it is quite rare. I own an unused example with printing on reverse showing that it was made in Chicago. 1 cents in the late 1800's was worth much more than now.