And it looks like even the Smithsonian may be mixed up on these... they list the date of the catalog as "1959", and then immediately below this they list "1959" again with a question mark. And altho they list the numbers of coins initially at 14 in the title area, further below they added "Supplement has subtitle - 18 gold coinages", which my Krause shows 18 as well... for the 1957 series. This, to me, suggests that the mint added 4 more leaders during the production run. As already mentioned, Krause left out entirely anything regarding 1958 (I have examples of the 1958's) and listed only one coin for 1959, a 1959 proof 50 gram medal. This whole series is nothing but one BIG question mark. thanks for the reference NPcoin.