Giant-Size Avengers #1 (Pt 29) Iron Man and Nuklo, The Invader That Time Forgot

Giant-Size Avengers 1 (1974) Buckler

Tales of Suspense 60 (1964) Kirby

The Kirby cover:

Tales of Suspense 60 (1964)

Ah, but you were probably already familiar with that Iron Man image; it was used as Shellhead's corner pic from 1967-1975. Examples:

Tales of Suspense 95 (1967)

Iron Man 68 (1974)

Giant-Size Avengers #1 (Pt 28) Scarlet Witch, Bothered and Bewildered

(l) 1974  Giant-Size Avengers #1 - Buckler
(r) 1971  Avengers #86 - Sal Buscema

Giant-Size Avengers #1 (Pt 27) Dr. Doom and Nuklo, The Invader That Time Forgot

Giant-Size Avengers #1 (1974) Buckler

Fantastic Four #57 (1966) Jack Kirby

Giant-Size Avengers #1 (Pt 26) Captain America Strikes Again!

GS Avengers 1 (1974) Buckler                             Tales of Suspense 94 (1967) Kirby

Giant-Size Avengers #1 (Pt 25) Scarlet Witch, Whizzer, Sue and Reed

Giant-Size Avengers #1 (1974) Rich Buckler

Fantastic Four #50 (1966) Jack Kirby

Giant-Size Avengers #1 (Pt 24) Captain America's Famous Red, White and Blue Garb

Giant-Size Avengers #1 (1974) Rich Buckler

Tales of Suspense #84 (1966) Jack Kirby

Giant-Size Avengers #1 (Pt 23) Scarlet Witch, Whizzer, Ben and Reed

Giant Size Avengers #1 (1974) Rich Buckler

Fantastic Four #78 (1968) Jack Kirby

Giant-Size Avengers #1 (Pt 22) Captain America and Mantis

Giant-Size Avengers #1 (1974) Rich Buckler

Tales of Suspense #85 (1967) Jack Kirby

Giant-Size Avengers #1 (Pt 21) What's Up, Doc?

Giant-Size Avengers #1 (1974) Buckler

Thor #171 (1969) Kirby

Giant-Size Avengers #1 (Pt 20) The Doctor Is In

        G-S Avengers 1 (1974) Buckler                Thor 174 (1970) Kirby               

And lol--he's lost some hair, but doesn't he look like the same doctor who treated Reed Richards in 1964? ;)

Fantastic Four 26 (1964) Kirby                  Giant-Size Avengers 1 (1974) Buckler

Giant-Size Avengers #1 (Pt 19) Magneto, Scarlet Witch and Quicksilver

Buckler's GSA #1 panel (r.) evokes the famous X-Men #4 cover.

                       X-Men #4 (1964)                                                                  

And yes, on the X-Men cover here (and on X-Men #5), Wanda the Scarlet Witch is clad in green. Back then Quicksilver was the one with a green costume, but on the cover he's miscolored in blue. 

Snappy Stan's response (in reply to reader's letter in X-Men #7 pointing out the incorrect colors on the covers): "Sometimes we change a costume's color on the cover to balance the design a bit."  So now you know!

Giant-Size Avengers #1 (Pt 18) Black Bolt and Vision

Giant-Size Avengers #1 (1974) Buckler                                              FF Annual #5 (1967) Kirby



And immediately following the panels above:

           

                       GSA #1 (1974)

             

FF Annual #5 (1967)

Giant-Size Avengers #1 (Pt 17) Thor's Stern Profile

GS Avengers 1 (1974) Buckler

Tales of Suspense 86 (1967) Kirby

               

Fantastic Four 31 (1965) Kirby--
Inspiration for Thor's GSA face?

Giant-Size Avengers #1 (Pt 16) Bill Everett/Sub-Mariner Tribute

                                                                           

GS Avengers #1 (1974) Buckler

Young Men #24 (1953) Bill Everett

Giant-Size Avengers #1 (Pt 15) Thor and Iron Man

This Kirby sequence from Avengers #6...

1964: Avengers #6  Jack Kirby

...is used in this panel sequence from Giant-Size Avengers #1. 

1974: Giant-Size Avengers #1 Rich Buckler

Giant-Size Avengers #1 (Pt 14) Jarvis 'n' Johnny

Giant-Size Avengers 1 (1974) Buckler

Fantastic Four 99 (1970) Kirby

Giant-Size Avengers #1 (Pt 13) Scarlet Witch and Invisible Woman

We've already seen the source for the Whizzer in More Classic Kirby, so today it's Wanda's turn--hip hip hooray! ;)

FF Annual #4 (1966) Kirby

GS Avengers #1 (1974) Buckler

The full Kirby panel from 1966's Fantastic Four Annual #4: 

Fantastic Four Annual #4 (1966) Jack Kirby

Giant-Size Avengers #1 (Pt 12) Thor and Nuklo, The Invader That Time Forgot

Giant-Size Avengers #1 (1974) Buckler

Thor #148 (1968) Kirby

Giant-Size Avengers #1 (Pt 11) Captain America's Ups and Downs

Giant-Size Avengers (1974) Buckler

Tales of Suspense 92 (1966) Kirby