The Nov. 14 installment of “Making Moderns” discussed the Special Mint Sets produced in 1965, 1966 and 1967. Yet, some 1964 issues exist with the SMS finish and they are among the most mysterious U.S. coins of the modern era.

According to Scott Schechter and Jeff Garrett’s book, 100 Greatest Modern U.S. Coins, 1964 coins with the SMS finish used from 1965 to 1967 surfaced in 1993 at a Stack’s auction.

On the mystery, the authors write, “There was no way to explain the existence of a 1964 Special Mint Set, as Proof coins were produced that year and no documentation concerning the creation of a 1964 Special Mint Set exists.”

What is consistent about all of the known examples is that they’re sharper and better produced than any regular 1964 circulation strike, but lack the Brilliant Proof finish of that year. Some auction lot descriptions have noted that the 1964 pieces lack the reflectivity seen on the 1965 SMS pieces. The majority of the 1964 SMS pieces that have survived are in exceptional condition.

Several theories have been put forth about their origin. The coins may have been produced as practice to assess the feasibility of production. They could have also been presentation coins issued to honor the final 90 percent silver coins or the introduction of the Kennedy half dollar.

While they may have been produced in 1964, some suggest that they may have been struck in early 1965, and a date of 1966 has also been proposed. Stack’s has noted that the set offered in 1993 was from the estate of a coin dealer. Speculation holds that they may have come from dealer Lester Merkin, who might have acquired them from a Mint employee, possibly former Mint Director Eva Adams. Adams was director from 1961 to 1969 and passed away in 1991.

With no mintage records, one can only use grading service population reports and instinct to estimate the population, but these coins continue to be rare. Most estimates place the mintage of 1964 SMS sets at 15 to 50 sets.

These coins are infrequently offered and their pricing is inconsistent. For example, an SMS 1964 Washington quarter dollar graded Mint State 66 SMS realized $1,265 at a 2009 Heritage sale, with other auction results for cent through quarter dollars cluster at the $3,000 to $4,000 range.

SMS 1964 Kennedy half dollars bring the highest prices. An MS-67 SMS example realized $16,100 in January 2010 and an MS-68 SMS piece realized $10,350 at an April 2009 Heritage auction.

The 1964 SMS coins are among the more enigmatic coins produced in the modern era. More may be out there, waiting to be discovered and confirmed by major grading services.

Steven Roach is associate editor of Coin World. Email him at sroach@coinworld.com.