I just received a "51" Special from an ebay purchase today.
It is Blue with a Lustraloy cap and clip.
Here is where it varies from my other Special-
On the barrel there is: MADE IN U.S.A 50. My other barrel has no imprint.
The barrel vent hole is in the end, rather than 2/3 of the way down, on the side.
It has a gold nib rather than a steel one.
It has a pearl jewel in the cap, rather than a black one.
The cap has only PARKER on the rim, rather than PARKER on one side and MADE IN U.S.A. and logo on the other side.
The filling instructions include: USE DRY WRITING SUPERCHROME INK. This is omitted on my other Special.

I'm guessing the Superchrome ink reference dates it, but I don't know the production dates for the ink.
Is the 50 a straight up date code of 1950?
Could this be an early "51" Special where Parker had not yet cranked up production on the steel nibs?

My other Special fits the profile on Richard's site.
Is this just a Frankenpen or what?

Jack

Post modified 'cause I'm a Printer, not a Proofreader.

The nib could have been changed at any point over the past 30 years?

I just looked at Richard's site again-
Could this be a Slender?
It fits the profile, but the filler unit is marked:
PARKER "51"
SPECIAL

And it is the hoop fille style.

I realize that during the course of it's 56 year life, any and all of the components that are oddball could have been replaced. My questions are more of the "If it is all original" variety.

By the by, I like it a lot and am very happy to add it to my little "51" group.

Jack