The 1870-S half dime is well-known as one of the few unique coins in the U.S. series and is a relatively modern entry into this exclusive club, being discovered only in the late 20th century. Heritage Auctions recently sold the piece as part of the Tom Bender collection, at the 2023 FUN sale, where it was graded PCGS MS64 CAC and realized $3.12 million.

The discovery story of the coin was not well publicized until Bill Burd, a longtime Chicagodealer, wrote in the June 1998 Numismatist:

So, where exactly was the Orland Park Coin and Stamp store located? This is a more complicated question that one might expect, as the business is long gone. A clip from the Blue Island Sun, September 11, 1977, reported:

This article placed the store in the Orland Square mall. Tom DeLorey, who worked at Harlan Berk Rare Coins in Chicago and lived in the in Orland Park area (Blue Island), wondered if the store was actually located in an adjacent mall (email to author, November 10, 2022):

I checked with the Orland Park, IL library regarding phone books from that period, and they had none. A second try, at the Newberry Library in Chicago, was more successful. A reference librarian at Newberry reported that phone books for 1979, 1982, and 1983 placed Orland Park Coin and Stamp at 412 Orland Square Shopping Center, on the north side of 151st Street. This was helpful, but didn't completely explain Tom's recollection, so I asked them to check successive years.

Newberry then reported that the store did in fact move and was listed in the 1987-1988 directory at 1120 Orland Park Place Mall, now on the south side of 151st.

As the 1870-S half dime first publicly appeared on exhibit at the 1978 ANA convention, prior to the move of Orland Park Coin and Stamp, we can thus pinpoint the of the coin to unit 412 of the Orland Square Mall, which is still standing.

Following the sale of the 1870-S half dime, the Storms apparently sold the Orland Park store and moved to Florida, as reported by the Numismatic News, April 2, 1983:

Tom DeLorey did one final piece of investigation and reported Of course, none of this explains who walked into the mall and sold the coin to the Storms in 1978, but at least we now know exactly where it happened.

To read the complete lot description, see:
1870-S H10C MS64 PCGS. CAC....(https://coins.ha.com/itm/seated-half-dimes/half-dimes/1870-s-h10c-ms64-pcgs-cac-pcgs-4397-/a/1356-3341.s)

For more information on the Liberty Seated Collectors Club, see:
http://www.lsccweb.org/