The stories in this issue were all probably originally published by Harvey. However, this issue inherits more directly from Sweethearts Library (Magazine Management, 1957? series) #56. On each comic story page, 'SL56' is initialed in one of the panels. And the reformatting of the original stories used in that publication is repeated here.
There is no date listed anywhere in the issue. The date used for the index is based the back cover where the photograph of Christopher Plummer indicates he is 'currently appearing in "Stage Struck"'. That film was released in March 1958.