Cover Art Check

There are some questions regarding the cover artists for these Doc Savage pulp covers. What are your thoughts?

I’ve groups the covers in question by who I propose was the actual cover artist.
In a couple of cases, I haven’t hazarded a guess on the artist’s name.

Modest Stein

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There are a few covers above not previously attributed to Stein. I think they fit his style.

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Unknown Artist 1

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Unknown Artist 2

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(Note: Mar-Apr 1948 has been attributed in the past to Edd Cartier.)

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Unknown Artist 3 – Charles Ravel?

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Do you agree/disagree with these groupings?