Hardy Boys Edition Identifier: The Secret Of The Caves

#	Years	Text	Cover	Spine	Art	EPs
A	1929-32	Original	Red	White	Rogers	Blank
B	1932		Brown			Brown Gretta
C	1932-40					Orange Gretta
E	1941-43			Yellow
F	1944-50				Scott
G	1951-59		Tan
I	1959					Brown multi scene
J	1960-62			Wrap	Nappi
K	1962-64		PC	Blue
L	1964-79	Revised				White multi scene
M	1979-87					Cameo
N	1987-Date		Flashlight PC			Blank
O	2017		New Art	Black	Bartlett
Major Variants 1959 - off-center cut, dark brown multi scene ep's 1962 - "$1 Box" on cover