"Made in germany" formula is still in use today. Fun fact: The british demanded that marking for their "Merchandise Marks Act 1887" (so they can boycott it properly?
Meanwhile, there was a split into "MADE IN W. GERMANY" and afaik "MADE IN GDR" you know when.
The change from 4 digit to 5 digit Post code was in 1993, if you want to use that for dating german things.