Mary's weight can be seen via this link
and the base with label via this one
As well as cropping out the section from Mary's original photos, I have tweaked the sharpness a bit.
As for Monart labels on PY weights, there are quite a few around and probably most that Paul made for sale via the Monart factory outlet(s) would have the label applied, but of course, labels can fall off or get damaged and removed. As Frank says, labels annotated with a "P/W No" are scarce. I know that Mary had (or still has) one - a damaged Dragonfly weight that I bid on in eBay some years ago.
And not that I am a "sour grapes" sort of person, but Mary has some rather nice Ysart items that I am almost jealous of.