I'd say late 80s - early 90s. Double edge was no longer the most sold thing in the Western world. That's when they deteriorated.That is what I remember. I have never thought that thd German blades were bad, but not the blade that I remembered.
As such, I was a bit disappointed. While they were not bad, I didn't see any thing special about them that set them aside from other modern blades, other than their more expensive $22/100 price.
They didn't seem to cut better, shave smoother or last longer. Though I couldn't find anything specifically about them to have issues with, neither could I find any thing particularly praise worthy about them.
Currently, I have both an Indian and a German blade out in rotation. Both happen to have 5-shaves each on them and the Gillette happens to be loaded in the R41 head for today's shave.
I think the biggest thing I was not aware of in returning to DE shaving was the lack of longetevity in modern blades. As such, I was over shaving the blade and would get razor burn for reasons that were unknown to me at the time.
I am currently in a quest, now that I have a greater variety of blades and have settled in on my basic procedures, to see if every blade will last a full week while still providing a top notch shave.
Currently the Gillette version's are $6/100 and the German ones are $18/100. For 1/3 the price, so far, the ones from India are giving me an excellent shave and an excellent shave for the dollar.
After the beginning of the year, my "inquiry" phase will have been concluded and I plan on a full week's rotation on each blade.
Which does have me bring up another point/question. At what point did the vintage blade longetivity of 2-3 week's go away to be replaced by 4-6 shaves?