Re: Paul Jokelson and removal of Monart labels ... my own thoughts on the matter ...
There are not many PY weights known with both a py cane and a Monart label and the very few examples I have seen could all easily be from the pre-Jokelson years.
But .. it was, apparently, the "exclusive" use of the py signature cane - not any particular label - that showed a Paul Ysart weight from the mid-50s onwards to be for the American market via Jokelson's distribution. So, on that basis, maybe they did have labels applied and maybe Jokelson did remove them?
There are many known unsigned PY weights that do have a Monart label and of the ones I have seen, several are very likely from the mid-50s at the time when Paul Jokelson had begun his contract with Paul Ysart.
I wonder whether Moncrieff's simply honoured the contract bewteen the two Pauls and, from that time, only added Monart labels to the unsigned, and hence non-American-specific, weights.