The signed vs. unsigned thing is not correct when taking into account at least 2 Parkings within the a VERY close (aka in between) range of case/mvmt serials, compared to others without signed crowns. The claim is a claim not a fact. Sorry.
The E858 is nowhere pictured in a vintage catalog as a Parking, to my knowledge at least, so two watches are not a proof in my understanding, more likely I find the idea those where pocketwatch dials. But ok, when legit as a wristwatch without a unique case reference, than I can build up a lovely 18k YG E858 with my spare NOS Parking disk. Haha. Oh no I can't, the disk has the right small diameter but a diamond style solid marker...
Nice PG, by the way.
acvocatus diaboli