Andre Norton - Daybreak-2250 A.D. paperbook book. This is an Ace edition from 1952, third printing.

Picture from Michele Curatola.

This cover is not likely to be 1952, given it is the third printing.

Comment from Stephen J West.

ACE c. 1952.

Picture and information from paperchase2000 via ebay.com.

75c coverprice suggests the late 1960s or early 1970s.

Comment from Stephen J West.

ACE double D-69.

Picture and information from ACE covers library .