The below is from the Appliance411 website
Note! This product could have been manufactured on multiple dates. Personal assistance may be needed to date the product more accurately.
According to the serial number this product may have been manufactured May of 1976 or 1986.
If the appliance's identification tag says "White Consolidated Industries" or "WCI", a suggested date after 1980 is likely correct. If it says "General Motors" the earlier date is likely correct.
Date code on identification tag
Additionally, the exact date of manufacture may actually be found printed right on the model and serial number tag. Look for a 4-digit date code (eg. MM/YY) printed on the identification label (see example above).