I realize that the filling systems are different for each type of Parker 51 pen, but I would be curious to know if (all things considered) nib size, etc. would a person notice the difference between the two when writing from these pens.

It would be very hard to isolate the effect of each filling system on the writing characteristics of the "51." You would need to test with the same nib, the same feed, same nib-feed adjustment, etc.

My gut feeling is that the other differences, the accidental differences of adjustment, would have more of an impact on how the pen writes. Similarly, I don't find any difference in the writing characteristics of the same cartridge/converter pen whether using cartridge or converter with the same ink.

The obvious "51" differences, cosmetics and "cool toy " factor are enough reason for most of us on FPN to own and write with both.

Andy

I must agree with Andy here. The nibs and collectors appear all but identical. The nibs are interchangable. The most incredible thing about the system is the amount of ink avalable to the nib.

It is a shame there is not a full-flex nib for the 51 that goes from extra fine to 4 Broad....

Ron

I have a Vac that I bought with a XF nib, which just did not do it for me, so I swapped that nib for an English Newhaven Medium nib. A nib type that I am very familiar with, having wrote with one since 1962 .

Having swapped out that nib, I can tell you that the 1946 Vac now writes pretty much the same as the 1950/60s era Aerometrics I have with the same type of nib.

So my answer would be, that if the pen is set up correctly and has a similar nib, you won't notice any difference.

Jim