How do I know when a German heat pump was manufactured?

Every German built heat pump uses the FD code (Fabrication Date) in the above format. For example, a heat pump with: 

FD8806 = 2008, June

FD9111 = 2011, November

FD9803 = 2018, March

FD0107 is 2021, July.

The date simply explains when the product was made, not when it was sold.