Lupin in the Green Jacket is probably one of the most famous versions, although it is the shortest series of the gentleman thief. In this first series we see a Lupin with certainly more noir tones than in the following series.
Less kind-hearted and more determined to achieve his goals.
The merits of this series are many: first of all it was one of the first cartoons intended for a mainly adult audience, which made the character immediately loved, even outside Japan, there is a great attention to detail, both in terms of weapons and equipment, and for the plans put in place by Lupin and his gang. The characters are multifaceted and each episode has been crafted with care.
However, being the first television transposition of the Monkey Punch comic, some flaws are inevitable. One of the most relevant is the alternation of several people to direct the episodes (including Hayao Miyazaki). The episodes are all more than enjoyable, but sometimes there is a bit of inconsistency in the style and some are slower and less exciting.
In conclusion I add that: certainly compared to the most recent Lupin films and series, the first series can be slower and more particular, as we see a darker and less light-hearted protagonist, but if you love Lupin (or excellent animated series) , I advise you to retrieve this series and also watch it for what it represented.
Enjoy your vision.