Apache Baseball Academy (found anime series; 1971-1972)
Apache Baseball Academy (アパッチ野球軍) is a 1971 anime made by Toei. The anime was adapted from a manga that ran in the now-defunct Weekly Shonen King.  This anime was famously directed in part by future Studio Ghibli director Isao Takahata.  It was released in Japan.
In it, an athlete grows up and decides to be a high school baseball coach instead of pursuing a professional career.  This paralleled a tension in the early Ghibli director's career, as his first feature at Toei in 1968 did poorly, and he eventually decided to shift his focus to anime for a younger audience with Hayao Miyazaki. The series had a short run of 26 episodes from October 6th, 1971, to March 29th, 1972.
Prior to January 2016, the series was solely available through a limited edition DVD set in Japan (valued in the thousands of US dollars) and some rumored fansub VHS tapes. However, Apache Baseball Academy was found on January 25th, 2016, and uploaded to nyaa.se torrents by user "hokuto_san." However, on May 1st, 2017, nyaa.se was deactivated by site owners over fears of legal troubles. The file links still exist on nyaa backups, like Pantsu and Nyaa.si. 
The entire series can now be downloaded via MEGA.
The following are some videos of early episodes uploaded to YouTube (by user "1971Happa6464").
- Ghibli blog article on series Retrieved 30 Jan '17
- MyAnimeList page Retrieved 30 Jan '17
- Isao Takahata's pre-Ghibli work in television Retrieved 30 Jan '17
- Nyaa.se torrent link. Retrieved 21 Oct '16
- Pantsu torrent link. Retrieved 3 May '17
- Nyaa.si torrent link. Retrieved 24 Aug '17
- MEGA link containing all 26 episodes mirrored from Nyaa.
- The YouTube channel with three raw episodes. Retrieved 21 Oct '16