These American Publishers Corp Library editions
are similar to the green and white APC library editions but have orange boards with a boxed in
picture on the cover. Unlike the green and white, they are not
drawn on the cover taking up most of the space. They are similar to the Magnifying/Nonmagnifying glass
library editions in that they have a boxed in picture fully screened on the cover.
On the back is the APC logo. Some have the Blue Multi-Pic II endpapers. The inside listing
inside Ringmaster's Secret is to Mystery of the
volume #38, so I would date this particular library edition to around the 1960's.
in mind, this listing might have been an outdated inner listing when this edition was made.
The particular picture used for the covers of these library editions is not from the cover art
of the story inside but the frontispiece from
Volume #30, Velvet Mask. You can nickname these the "Velvet Mask" library editions!