Possible Clues:

• Before 1939, say
• About in the warp before the fighting before now
• Period before hostilities
• More brutal power on the rise in the thirties
• Like the '30s, say
• More green power arises in advance of strife
• Like 1930s prices
• From the 1930s, say
• Penny prize defective in Edwardian times
• Prior to a major conflict