Thursday Story Strip Day.
I have shown a longer story form the start of this detective strip a couple of years ago, but here are a couple of the later months. Here's what Alan Holtz has in the credits:
Mike Roy: 11/26/56 - 7/6/57
Pete Hoffman: 7/8/57 (signed fill-in strip)
Unsigned: 7/9 - 7/13/57 (does not appear to be any of the other artists)
Fran Matera: 7/15 - 8/24/57
Ed Herron and Jim Christiansen: 8/26/57 - 3/1/58
Note that Ed Herron, who may have been handling the writing chores from the beginning of the strip, didn't get credit until Christiansen came on board. Mike Roy recalled, however, that John Broome did the uncredited writing, and was replaced by Ed Herron. He also said that Mike Peppe did inking on the series (during Roy's tenure only I presume).