This was the first Lupin the 3rd TV series aka The Green Jacket series, cause Lupin wears a green jacket.
After the making of the pilot film of 1969, this TV program was promoted to air with the help of TMS Entertainment(which has been producing Lupin anime for more than 30 years now).
Unlike the second TV series, that everyone's familiar with, this one has a more serious tone to it. Due to that, it received low ratings, so the later ones had a little more humor to it, which almost equals to the humor from the Red Jacket series.
It aired from 1971-1972. With a total of 23 episodes. Meant to end with 26 episodes, but it was canceled before any other episodes were put in production.
The animation is decent since it was made 34 years ago. The episodes done by Takahata and Miyazaki are the best ones. But too bad it only lasted for 1 season. Luckily over the years of reruns it received a fan base, and demands for more Lupin were made. It came back as the Red Jacket series which lasted longer than this one.
What's cool about the Green Jacket series was it was the first anime aimed for Mature Audiences.
Due to it having nudity, violence, and some drug use. i recommend it for teens and older.
Those who like Lupin the 3rd can check this series out. There's no word on this series being dubbed yet, but my advice is to search this series on Bittorrent or a Fansub shop if you're lucky enough.
