This issue has variants.
This issue is bannered "Anniversary Celebrating Batman's 600th Appearance in Detective Comics" even though it is actually the 601st appearance in Detective Comics.
This article, appearing on the inside front cover, explains the structure of the issue: a reprint of Batman's first appearance, a reprint of the story Julius Schwartz commissioned to commemorate Batman's thirtieth anniversary, and two new stories using the same plot as the others created by the then-current creative teams of Batman and Detective Comics.
This is not a reprint of this story as originally published. Instead, it is a redrawn (traced), re-lettered, and censored copy which originally appeared in Detective Comics 387. A notable change is that the murder victim on page 2, panel 2 does not have a knife jutting out of his back, as he did in the originally-published version of this story.
New story, commissioned by Julius Schwartz in celebration of Batman's thirtieth anniversary, which re-uses the plot of "Case of the Chemical Syndicate" from Detective Comics #27. Credits for script, pencils and inks confirmed from Julius Schwartz's editorial records, provided by DC Comics. The original story is 16.67 pages long; this reprint fills in the final 0.33 page with a caption box ("Several significant changes were made, of course...").
New story re-using the plot of "Case of the Chemical Syndicate" from Detective Comics #27. Story is dedicated to "Bob Kane and Bill Finger and all those others who have kept the legend alive."
New story re-using the plot of "Case of the Chemical Syndicate" from Detective Comics #27. The final two-page spread of this story shows Batman swinging above images of his friends and foes with the number 600 super-imposed over the Bat-Signal behind him along with two caption boxes concluding the narration from the story.