With the release of the Spielberg Tintin film, I've been thinking of the 1960s series produced in Brussels by Belvision studio.
7 of the storylines were adapted to animation, which was presented in cliff-hanger format for a total of 50 five-minute shorts. They were subsequently imported to USA, where the voices were dubbed over by veteran actors Dal McKennon and Paul Frees.
But as it turns out, one of the storylines was animated in USA. A Cartoon Brew post on various adaptations of Tintin over the years led to a comment from Philippe Capart, who made a documentary about Belvision. The first story to be adapted to animation was "Objective Moon", produced in 1959. Belvision contracted with America's Larry Harmon Studio to produce the storyline. Harmon's studio has experience in mass-producing TV cartoons, making Bozo the Clown cartoons for syndication and also on the King Features Popeye series.
The Belvision series has poor reputation amongst Tintin fans. While I don't think the series in general is that bad, the case can be made for this one. Harmon's studio has made some really bad cartoons. The drawings are pretty poor and the writing could've been better. Subsequent storylines were animated in-house at Belvision with their own artists, although Charles Shows stuck around doing all the voices.
Voices are Larry Harmon (Tintin, Professor Calculus) and Paul Frees (Captain Haddock, Thomson/Thompson twins). Paul Fennell directs. Lou Scheimer, who went on to start Filmation, did the backgrounds.