I think that the earlier examples, with better quality, can easily be thought to be ok, even with a "slipped Y" in the signature cane. Also, some of those earlier false "py" canes can appear to have the same colour for both letters and only close scrutiny will show the reality.
The later flase "py" canes, with the smaller and more balanced letters, usually show the colour difference in the letters more obviously, but some can be hard to spot. Although the general quality of the later batch is poorer, unless people have seen genuine PY weights, it can be easy to asume that they are really good. But in truth, they almost always show some element that looks a bit "iffy" for a maker like Paul Ysart.
I have seen maybe three other examples of the "roundels" design from the earlier batch and I think only one was for sale. A possible regular feature of the roundels (or cane group?) design in the non-Ysart examples is that the "py" cane is included as one of the roundel canes and as far as I know Paul Ysart never did that -if he added a signature cane within the design it would have been set discretely against a roundel (or group) or perhaps placed in the centre. (But don't quote me on that as being 100% true.)