One of the two US commemorative coin programs for 1998 was the Robert F. Kennedy Silver Dollar program (the other was the Black Revolutionary War Patriots Silver Dollar). The coin was struck to commemorate the "life and work" of Robert Francis Kennedy (RFK). Robert, as was his brother, John Fitzgerald Kennedy, was assassinated. In Robert's case, it was in Los Angeles, CA on June 5, 1968, just after he left a party celebrating his victory in the California primary for the Democrat presidential nomination.
The RFK silver dollar was released in Proof and Uncirculated finishes, with the majority of the Unicrculated coins taking on a satiny appearance (I have seen some with a more brilliant finish, but they appear to be in the minority).
A special set - the Kennedy Collector's Set - was created in addition to the standalone coins. The Set combined the Uncirculated RFK dollar with a matte-finish JFK 90% silver half dollar. To indicate its special finish, the Set's half dollar is graded as a Specimen ("SP") coin by the major grading services. Some PCGS holders add "SMS" which is an acronym for "Special Mint Set," but this is a misnomer and shouldn't be confused with the 1965-67 Special Mint Sets issued in lieu of Proof Sets. Only the 1998-S half dollar had the special matte finish (no other 1998 circulating denominations were struck with it) vs. the 1965-67 sets for which coins of all circulating denominations had a special finish.
To achieve the satiny finish, the faces of the dies used to strike the silver half dollars were first sandblasted with a mix of glass beads and aluminum oxide, and were then plated with chrome to harden them.
The finishes of the two coins in the Set were very similar in appearance enabling the two coins to match well. The issue price for the Kennedy Collector's Set was $59.95. (The Set should not be confused with a US Mint-issued, two-piece set that featured Proof and Uncirculated versions of the RFK silver dollar.)
The Set was produced using a mint-to-demand model. Orders for the Set received between January 2 and February 13, 1998 established the mintage level for the Set. Per Mint records, 64,141 units of the Collector's Set were sold. For the Uncirculated RFK silver dollar, the total is just part of the 106,422 total Unirculated units sold. For the matte-finish half dollar, however, the 64,141 pieces represents the full mintage.
Due to its inclusion of a low-mintage matte-finish Kennedy Half Dollar, the Set continues to command a premium over its issue price, though the premium has lessened over the years. While many sellers still look to get $150 to $200+ for the Sets, they can also be found for less than $150.
I bought my Set in the aftermarket a number of years ago and paid under $150.00; better deals are likely out there.
1998 Kennedy Collector's Set
(Image Credit: US Mint, Media Image.)1998 Robert F. Kennedy Silver Dollar
1998-S John F. Kennedy Half Dollar - Matte Finish

For more of my topics on commemorative coins and medals, including other Modern US Commemorative stories, see:
Commems Collection.