[Mr. Izaj]

 Very likely the former because he along with Mike Esposito were among those "go-to" inkers that often got assignments when a deadline was pressing. You have to remember that a lot of comic book publishers wanted artists who could efficiently meet deadlines, particularly if they needed material that had to go to press right away.
 
  In fact Mike Esposito and his frequent collaborator, penciller Ross Andru were Robert Kanigher's go-to artists when he needed a story for one of his books when there was a serious deadline pressing. The best known example of that occuring occured in 1962 when Kanigher needed to fill an issue of Showcase in just two weeks before it was due at the printer. He wrote a book-length story over the weekend and then gave it to Andru and Esposito to pencil and ink it. They managed to get the whole project to the printer with days to spare. That story was the first appearence of The Metal Men which appeared in Showcase #37 (March-April, 1962).