I'm not in the mod to do it for you, but I think you'll find the answer to your question here:
the hub-dates
Thanks for the answer!
According to
http://www.torpedo-coasterbrake.com/hub-date.htm “On hubs made from 1975 to 1989, you will find 2 letters on the brake lever. The one above is for the month.”
On my brake lever the letter above (for the month) is U. How to translate it to a certain month, since U is the 21st letter (or 19th excluding J and Q)?