After some phone calls to NBS and Naval Observatory, I found out that there have been 14 leap seconds inserted.

1) 1972 Jun 30 23:59:60 # NBS Special Publication #432 ... 14) 1987 Dec 31 23:59:60 # Naval Observatory

Which, providentially, agrees with the data in the comp.sources.unix posting. Hats off to bww and guy! --ado