To determine the production date of a heater, examine the following field on the rating plate: F.år. The four letters refer to the production year and week based on the following table. In the picture below, you can see how you find the right field on the rating plate.
Here is an example of the production date field on the heater’s rating plate.
B G B B = 1611. The heater was manufactured in year 16, week 11