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I immediately recognized the model for Thundra's very distinctive pose...  
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| Giant-Size Super-Stars 1 (1974) Buckler              Journey Into Mystery 122 (1965) Kirby | 
 ....and then I came upon other panels from that same page of Journey Into Mystery #122. 
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| Giant-Size Super-Stars 1 (1974) Buckler              Journey Into Mystery 122 (1965) Kirby | 
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| Giant-Size Super-Stars 1 (1974) Buckler     Journey Into Mystery 122 (1965) Kirby 
 
 
 
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                 Plus! This GSSS panel from a nearby page is also based on the same JiM #122 sequence as above. 
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| Giant-Size Super-Stars 1 (1974) Buckler | 
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| Journey Into Mystery 122 (1965) Kirby | 
The pages in question:
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| Panels from pages 2 and 3 from Journey Into Mystery #122 ... 
 
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| ...are used as templates for panels on page 19 (l.)  and page 27 (r.) in Giant-Size Super-Stars #1.
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