I was commenting on the method to create the artwork, not what it was ultimately used for. None of the 3 images (Karloff, Lanchester or Hobson) look to be photographs or offset printing, imo. What does it look like to you?
ps- Even tho this artwork was used on a pressbook cover, isn't this also an insert?
No, this was not used as the insert, 3-sheet, or window card (though all 3 use a similar design and layout), this is unique to the pressbook.
The insert does give the best view of all 3 photos that were used in the design of the pressbook cover, ranging from the tinted-photo of Hobson to the full-on artwork of Lanchester.