Here is an example of a pre 85 in silver plating. You can see the head is chromed still but the handle is silver plated.
If this instruction sheet is any indication we can say at least 1953 as a precursor date for the Walbusch B5 razor. I'll dig some more but I am going to go with the B5 is a post WWII design and no earlier.
Here is another interesting Progress made for sure in the early 90s. What makes it interesting is they went back to the knobs with dots between the numbers like the earlier models in 50s and 60s and possibly later into the 70s. The other is the logo stamp, this one is obviously after the German reunification in 90 and instead of changing the molds they were using that said W. Germany they modified the same mold to obfiscate the W. 2016 is when they changed from this to the modern mold they are currently using for the razor heads. This one is from 1990/91 - 2011 assuming they switched to this style knob right away if not sometime after 90/91 but definitely by 2007 -2011. This one is from 2012 - 2016, only major change is the knob went back to hash marks instead of dots between the numbers on the adjustment knob. If the second statement above is true then 90/91 to about 2007 then 2012 - 2016. These dates were ascertained by studying various youtube videos featuring a Merkur Progress going back as far as 15 years ago.
