Hello Baz69, I think this is a tough question as eg. one of the manufacturer known for their most prolific use of yellow grips, WKC, can hardly be put into a special age section as their mm did not change during the IIIR period. Also WKC hardly did change the material for their daggers.
Sorry, I personally could not answer your question.
Regards,

wotan, gd.c-b#105

"Never look for sqare eggs" as a late owner of an original FHH-dagger used to say.