"Attached is a listing of the die stampings found on the engine side of the radiator top tank. Please note, this is not necessarily the part number. Year and month of production are usually found above this part stamping with the year denoted as two numbers and the month as a letter e.g. 46 G would 1946 month 6 or June."

https://www.thebrassworks.net/harrison-radiator-part-stampings.html