I could understand that, if each was made in a different Rubycon factory, then there could be some slight variation in tooling/equipment used to stamp the vent or print the markings.
However, I would not expect the font of "PK" to be different between factories. Would think the sleeving artwork would be consistent.
You can try to take the capacitors apart, unroll them, and see if anything looks vastly different. To be honest, most capacitors I've unrolled look basically the same, so you'd have to look hard for small details.