From the vintage Panasonic site: "
How can I tell what year my Panasonic bicycle is?
Typically, the lower part of the head tube or the bottom of the bottom bracket shell will contain a number. The first number and letter are what you should look for. Example: 7K02143 The first number designates the year (1987 in this case) and the letter designates the month of manufacture (K = 11th month, therefore November). "
Your serial number doesn't quite follow that pattern, but is close. I would look for a number in front of the E.
For anyone into Panasonic bikes (like me), this is an excellent site:
http://panasonicbikemuseum.info/
FWIW, my four Panasonics in the keeper fleet, are all SCHWINNS.
Tange also often put a date code on their forks (on the steering tube).