Somebody scanned and posted JPEGs of Charlton Comics’ “The Comic Book Guide for the Artist • Writer • Letterer” from 1973. I made a handy-dandy PDF of the images for easier consumption. Download it if you wish; it even includes the old Code of the Comic Magazine Association of America, which is a great read if you are old enough to remember when comics had “Comic Code Approved!” on the covers. Very cool.
Charlton Comic Guide (6.8 MB PDF)