There are numerous reasons and metallic composition would play a role. Perhaps the largest single reason is the relationship between supply and demand. There are around 750,000 casual collectors of Kennedys and another 50,000 more serious ones. This puts a stress of sorts on the availability of the '70-D but a much lower stress on the '87 issues. It is quite easy still to find quantities of the '87 mint sets but the days of finding lots of '70 sets are long gone. Many of the '70 sets that survive have very poor quality half dollars because the better ones are in collections and time has not been kind to the surfaces of these coins. The '87 issues are mostly still pristine and there has not been extensive cherry picking yet. Your mintage figure is a little low as well. These also appeared in the souvenir mint sets and these mintages got lost in a limbo somewhere. In those days mint set totals were included in regular production run totals and reported separately. Souvenir set totals were also included but not reported. It's not known how many of these were made but 100,000 of each should be in the ballpark.
Curiously, gem '70-D Kennedys are not especially difficult to come by. Around 3% of the mintage was of gem quality. The '87 issues are far tougher yet don't command much more. This is likely because new collectors can still find their own '87 gems because of the availability of sets but the '70 gems are very elusive because of attrition and cherry picking.
As time goes on this pricing structure should evolve to more closely approximate their relative availability.
Time don't fly, it bounds and leaps.
Posted 08/05/2006 7:23 pm
