I ran across this cover that looks pretty cool, by Arthur Adams. I thought it looked familiar, and might be a tribute cover, based on Barry Windsor-Smith's 1972 cover... and it is. And I was curious whether it was a commission page, or an actual cover or variant cover for an AVENGERS issue. And it is.
Variant cover 10-F of that AVENGERS series. After quite a few re-booted AVENGERS new series, where they each started over with a new number 1, and multiple times after-the-fact, editors and creative teams went back and counted out again, re-establishing the "legacy numbering" extending from the original 402 or so issues of the first AVENGERS series, to determine this was issue 700. Hence, the specially commissioned cover by Arthur Adams. It's yet another example where you almost need a PhD in comics continuity to follow what they're doing with this issue.
It's issue 10 of the 8th AVENGERS series, variant cover F, but with some bending and twisting through the multiple series, it's issue 700 if you very carefully count through all those AVENGERS series. And the variant covers on issue 10 go ( A, B, C, D... ) up through "L", halfway through the damn alphabet numbering all the variant covers !! At least there was one good one by Arthur Adams.
And here's the first AVENGERS series, and the issue 100 cover, that Arthur Adams' cover is tribute to :
It looks to me like it was a commission page Arthur Adams did on his own in 2013, that some editor at Marvel found out about in 2019, and said what the hell, let's buy and use it as a variant cover for issue 700.
Barry Windsor-Smith (back then just Barry Smith) also did AVENGERS issues 66-67, and 98-100.