That is a good weight; clear, clean & crisp-looking. (Good photos, too.) But there is a "fault"!
The inner ring of red-white canes has only one which is the "proper" shape, the rest are "squashed" in a variety of ways. Clearly, for the overall look of the weight, that "fault" does not detract too much. And it was just an accident of the way most of those particular canes reacted during the working. It was not so much of a problem that the weight should not be put out to the market.
It is an example of a weight that has good features but a small area of lesser quality. And that, I think applies to many Paul Ysart weights throughout his Moncrieff period. I do not believe there was a time when suddenly he got everything right and never had a problem thereafter. There are lots of examples of apparently pre-war period PY weights that have very little, if any, defects in the working - except for the "darkened glass" of the dome. And there are many apparently post-war Moncrieff examples that have clear glass domes but have an "error" somewhere.
So I tend to think that a dividing line, such as pre- and post-war periods, marking different quality levels does not really exist. More likely that there was steady progress and improvement across all those years but, on occasion, some weights, even though good enough for the market at the time, did not show the absolute best quality.