I'm beginning to get a little interested in Parker 51s, despite having always been a dyed-in-the-wool modern pen type of person. There seem to be Vac-fill 51s and Aerometric. Are the Vac-fill pens the same as Vacumatic? And, more importantly, what are the differences? Where can I find a reference on this? Which works better over the long haul? Which is more serviceable? Is there a knowledgeable consensus about the pros and cons of each style?

I would look at Richard Binder's site for a fairly comprehensive reference on the Parker 51. In short, though, the Vacumatic 51s and the Parker Vacumatic use the same filling system. The Vacumatic 51s and Aerometric 51s are fairly similar, but I believe that the dimensions might be a hair different.

Usually people shorten Vacumatic to Vac. Sheaffer's on the other hand, created the Vacuum-Fil pen, which people shorten to Vac-Fil. Richard's website is definitely a great spot to look at for reference.

Evan

As far as "better" goes, it depends on your definition. Aeros appear to be nigh-indestrucible filling systems, but have a lesser ink capacity than the vacs and are slightly less cool through being more numerous. Vacs have a fiddly filling system that needs occasional replacement of a regularly-stressed rubber component by someone who has the right skills/tools, but as mentioned before hold VAST amounts of ink. The writing end of it, as far as I know, doesn't notice the difference in where it's getting its ink from. If you're after ease of maintenance, the aero has a small edge.

ps-- the design was all new in 1941. To a lot of us, that lands it firmly in the category of "modern pen".

If I were stuck with only one pen for the rest of my life, and no possibility of repair my pen of choice would be a "51" aero. Simple and bulletproof. IMHO, the vacs hold more appeal for the pump at the end, double jewel design (on some) and just more fun. The caveat is that they are almost impossible to flush, so find an ink you like and stick with it. The aeros are much easier in this regard. What everyone else said about checking the reference section of Richard's page is your best bet. I'd also check Ernesto's page on Parker "51"s as he's one of the leading authorities on the subject. His site is www.parker51.com. Good luck. Your Borg ID number will be assigned once fully assimilated.

Thanks to all for the helpful info. Not that you should stop; it's been helpful so far, so please keep contributing
No kidding. I used to consider posting something vaguely disdainful about the groupthink toward 51s, and now I look down and see my fingers helplessly dialing up more Internet info on the damn things. In one week I've gone from thinking, "I really don't like the styling" to wondering about the differences between the 51 Aero Mark I and Mark II, and whether I want an early flighter or not, and whether I'll know enough next week to make an informed purchase. And all this time, I thought I wanted a Namiki Bamboo.... Resistance is futile.

Sadly, it's hard to beat a "51" for writing performance. My only real complaint is that the nibs require replacement on many of them, so my Sheaffer's actually write better (and yo will find many people who prefer them to "51"s for that reason).

Bet you can't stop with just one though!

Peter

jnb1061, I used to feel the same way. I wanted threaded caps and big nibs and couldn't see what all the fuss was about. Then I got a call from a local flea market owner that she had some pens for sale and to come on down. I joked to my girlfriend that I might find one of those mysteriously fabulous 51's there and laughed.

There was no 51 but there was a 21 all gummed up and unusable. The design intrigued me and after getting it up and running so I could write with it I knew the design was one I wanted to pursue.
Go figure.

There are a number of threads expousing the virtues of 51 aeros vs vacs. Most 51 collectors have and use both. The nibs and collectors are pretty much the same and you can find great writing pens in both. The aeros typically require less maintanence, but a new diaphram on a vac every decade or so isn't that much of a hardship. Beyond that, go for what you like. Vacs have more cap varieties while aeros offer more body colors. For a premium, double jewels (vac) or flighters (aero) are particularly sharp. In all likelihood you won't be satisfied with just one... Jeff

My experience is that I have never had to replace a "51" nib.
I have had them resacked, diaphragmed, and had breather tubes replaced or re-installed.
I've never had to replace a nib.

Just another's experience.

Yep I've never had a nib problem with my "51"s. Assuming the breather tube in an aero is intact (and that is more of an issue than you might think - if you don't get bubbles on at least 4 presses you likely have some detrioration) an aero with modern non-corrosive inks does seem to be a more hardy design. However, having gone through replacing a breather tube in an aero that had deteriorated it is a huge pain in the you know what, parts are scarce (I believe Ron Zorn and Richard Binder can fabricate new ones using surgical steel and a special jig to drill the tiny hole at the top which makes it a true aerometric replacement) and removal of the remaining tube if it has broken off close to the feed is also a nuisance (David Nishimura is one source for parts and a nice set of instructions on the replacement, but it is still not for the novice). In other words, having gone through that I'm less inclined to say off the bat that an aero is a home run more durable system. And there area lot of folks who can competently replace a Vac filler and get a pen working again quickly, for a lot of years, at a reasonable price.

At this point I assume any "51" - aero or vac fill - unless specifically stated it has been restored will require a trip to Ron, Richard or Tom Mullane for a restoration.