Kynoch Express cartridges

I have read many times that Kynoch stop making ammo for nitro express rifles about 1960.
I need some information about that.
Did they make it officially? I mean, was there a note or an add?

Its hard to put a precise date on when they stopped because by then they were only making most calibres on an occasional basis, having a production run of something like .404, producing enough for several years and storing it. It was still around in the early 70s in quite some quantity because I was working on a casual basis for Holland and Holland by then and it was still coming through.