Doraemon (partially found first-adaptation anime series; 1973)
Doraemon is a popular and long running anime based upon the manga of the same name that originally ran from 1979 until 2005 and a second series which began airing about a month after the conclusion of the 1979 series is still airing to this day.
However, the first attempt to adapt Doraemon to television occurred in 1973, when a Tokyo Movie Shinsa-produced (but animated by Nihon Hoso Eigasha) aired on the Nippon TV network. The series aired from April 1st 1973 until September 30th 1973 for 26 episodes. Unfortunately, the series was not popular with either general viewers or fans of the original comic, relegating Doraemon to remain exclusively in the manga format until 1979.
Also unfortunately, sometime in the 1980s, a "cremation" fire organised by Nippon TV destroyed almost all footage from the series. No episodes were thought to have survived (unless a rerun was recorded on VHS, as the show was in reruns until 1980), but the opening and ending credits do exist, as does some other footage, which is occasionally shown at Doraemon fan conventions in Japan. In addition, 21 episodes exist out of the 52 made, 2 without audio. Most of these are still images, but some actual moving animations are included.