In the tail end of the 30s, the Fox Syndicate of comic book publishing was, for the most part, Will Eisner. He wrote so many stories under so many different pen-names it is stunning. K-51 is one of his creations.
Fox released a new line of comics called Wonder Comics
in the spring of 1939. One of the many tales in this anthology was that of an operative named K-5. It was a quite short story with a fair amount of action in it, produced by Ned Coe, one of Eisner's aliases. The next issue of the magazine, one month later, had K-5 replaced by K-51 and the "author" was now Willie B. Rensie, another Eisner incarnations. The K-5 story had the tag line of "Spies at War". The first K-51 did not have that tag but subsequent ones for K-51 did.
Was K-5 really K-51? Why the switch in codename? Why the switch in writer names? Why the switch in the general feel of the story (my opinion)? Who knows!?!
One month after K-51 usurped K-5's position in the magazine, the name of the magazine itself changed from Wonder
though the numbering continued on from 2 to 3.
One interesting tidbit about the Wonder/Wonderworld
comics. The first issue had the lead character being a creation of Eisner named Wonder Man (hence the name of the comic). Immediately DC brought suit against Fox for copyright infringement. Wonder Man is seen leaping over tall buildings like Superman had already done. "Too close" claimed DC. "Not so!" denied Eisner. Eisner lost and the character vanished with only the one outing. The comic continued with the second issue having the lead character being Yarko the Great but after that, possibly to avoid further complications, the title changed to Wonderworld
and though Yarko would still be a part of it, it introduced The Flame
Just as Wonder Man came and went with the first issue, so did K-5. I personally do not consider K-5 being the same as K-51. Just an opinion. However, since they were in the same comic line and the name is so close and so on, I include the sole K-5 story in the line-up, with that caveat. Wonderworld Comics
would continue until issue #33 but K-51's missions ended with #27.
Note: Titles in quotes are mine. Titles not in quotes come from those given on Comic Books Plus
and I liked them.