My, how unusual! I know what WK means but are some of the other stamps Italian proof marks?

That is the first and only rib I have seen marked that way. Further, it does not have the Parker roll-matting on the gtop rib. How strange! I wonder what the "story" is with this Parker.

It definately appears to be new production barrels. Possibly reusing a few parts, like the locking lugs and such. But, there does not seem to be any sign of sleeving.
The rib does not look original to me. The font of the marking is larger and not correct style to be original. Also, the opening in the matting (for the letters) looks to be larger than normal. I think that the rib was just the barrel makers reasonable attempt at recreating the parker markings.

I do not think, off the top of my head, that Parker ever abreviated Meriden as "MER". Who knows why they chose to use ACME as the steel name on this set.

The WK seems to be applied by the maker of the new barrels.

Lots of people incorrectly say 'Meridian' in stead of Meriden. Luigi figured he was safe just saying MER.