That last post got me curious, so I went to check. Marvel Comics Group only became listed as the publisher of Avengers in 1973, a full ten years after the series had been launched. For the first 58 issues, it was officially published by “Vista Publications, Inc.” – a publisher which just happened to have the same address as the Marvel Comics offices, unsurprisingly – with absolutely no mention of Marvel Comics anywhere outside of the logo on the cover.
For #59, Avengers was published by “Perfect Film & Chemical Corp.” although the copyright is shared between that company and “Marvel Comics Group,” receiving its first indicia mention.
Starting with #60 and running through #109, the comic was published by “Magazine Management Co.,” which shared the copyright with Marvel Comics Group. #110 is when Marvel Comics officially becomes the publisher of the series.
I seem to remember reading somewhere – maybe The Secret History of Marvel Comics? – about Martin Goodman’s love of happily swapping out shell companies in order to work the books in his favor, but I have to admit, I hadn’t realized it went on so late into the success of Marvel as a brand.