Parker 51 Mkii Or Mkiii

February 11, 2016

Is there much difference between the P51 MKII and the MKIII ?

I just bought a MKIII and was wondering if the MKII was a preferred model or not.

Edited February 11, 2016 by Mangrove Jack

February 12, 2016

My understanding is that the MkIII model takes cartridges (basically the same type of fill system as Parker 45s, so also would take a squeeze style converter like on 45s). Beyond that, not sure.

I have one 51 that I have been told is a "late" MkII from the early 1960s -- so presumably it has a true Aerometric system the way my other Aeros -- a 1949 Plum Demi, and a couple pre-1957 ones (one Teal and one Black) do.

Ruth Morrisson aka inkstainedruth

February 12, 2016

The following information was copied from here: http://www.richardspens.com/

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The most common Aero-metric “51” is the Mark I. Externally, this pen is identical to the Vacumatic-filling version except that the barrel no longer ends in a blind cap and that the Split Arrow clip is gone, replaced by the plainer Arrow clip:

The filler in a Mark I pen has a plastic end cap:

A subtlety to watch for, however, is the filler of the “51” Demi. Early Slender pens, before the model was renamed the Demi, have fillers like that of the standard model; but later Demis, beginning probably in mid-1950, use the less costly “hoop” filler design introduced in 1948 on the “21”:

At some point, probably in the late 1950s, Parker introduced a slight variation on the Mark I design. In this apparently undocumented “Mark Ia” version, the Aero-metric vent hole is moved from the end of the barrel to the side of the barrel, about 2/3 of the way from the clutch ring to the end.

In the mid-1960s, Parker began producing the Mark II “51”. This version, redesigned to update its look, bears a noticeable resemblance to the 61. Its cap has a 61-style clutch, with fingers bearing on the shell instead of on the clutch ring, but the standard “51” clip is still present. The end of the barrel is squared off to a shallow conical shape that mimics the cone of the cap jewel:

Internally there are significant differences, as Parker redesigned the internal parts to simplify the sac guard and replace the costly machined collector and feed with molded plastic parts. The most noticeable internal change is in the sac guard, now a single piece of metal with its end formed closed instead of being capped by plastic:

The Mark III “51” appeared in about 1969. This pen looks similar to the Mark II. The cap shows the most visible external change. The clip, a new 61-style long Arrow clip, is no longer part of the cap’s decorative trim ring; it is a separate part. The trim ring and jewel are combined into a decorative clip screw that holds the clip in place as on the Parker 75. The clutch ring, which is not functional, is now reduced to a narrow trim ring. The most significant changes are not visible to the user:

No longer does the pen have the Aero-metric filling system. Instead, it has a short breather tube and is thus an ordinary squeeze filler like the “51” Special and the “21”.

The Mark III, unlike its predecessors, is made of an injection-moldable plastic, not Lucite. The new plastic is softer and will take scratches more readily; and it also can shrink over time.

The Mark III’s sac guard looks like that on the Mark II, but the trim ring identifies the later pen. You can also see on closer examination that the threads on the Mark III’s connector are rather coarser than those on earlier pens and that they have an Acme profile (flat on the crown and at the root).

Note that not all of the differences may be identifiable on any given pen; Parker phased some of the changes in rather than making a sudden 100% switch. The clip design of the Mark III is one example of this; there exist Mark III pens with the older design having a separate celluloid jewel.

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Best regards.

February 12, 2016

I dnot understand this mk thing. Beside true mki pens ;

I have mki pens with caps having 4 finger open clutch but with all other details as those of mki pen caps (jewel, clip etc).

I have pens with short but round ended barrels (standard size not demi) like those on mki pens but with clutch ring like the one on mkii and with 61 like caps (4 finger open clutch) but with short mki like clips and small jewel.

And I have pens with 4 finger open clutch ring, square ended barrels, mkii like clutch ring and 61 like caps with cut in the cap where the clip sits. The clip is fitted with a decorative P45 like screw.

And I have pens with square ended barrels, open 4 finget clutch, mkii like clutch ring, 61 like caps and domed cap screws.

Now what pen is what MK?

February 13, 2016

I dnot understand this mk thing. Beside true mki pens ;
I have mki pens with caps having 4 finger open clutch but with all other details as those of mki pen caps (jewel, clip etc).
I have pens with short but round ended barrels (standard size not demi) like those on mki pens but with clutch ring like the one on mkii and with 61 like caps (4 finger open clutch) but with short mki like clips and small jewel.
And I have pens with 4 finger open clutch ring, square ended barrels, mkii like clutch ring and 61 like caps with cut in the cap where the clip sits. The clip is fitted with a decorative P45 like screw.
And I have pens with square ended barrels, open 4 finget clutch, mkii like clutch ring, 61 like caps and domed cap screws.
Now what pen is what MK?

Sometimes what happens is parts get swapped around. Fairly common with caps. Another example would be a hood from a Super 21 landing on a Demi 51.