I won this on an ebay auction a while back and can't find anything about this type. Is it a vac or aero. cap? Is it rare? It is a gold filled cap with 8 parallels rings on it. I would appreciate any information, regards, John

I have tried taking a couple of pictures and can't seem to get a decent one because of glare. The cap is smooth except for the equally spaced rings.

Do you have a pic of the pen? Or maybe a link to the image?

Hi John, can you post a pic of the pen or perhaps a link to see it?

Here are a couple of good reference links on the caps of the Parker "51"

http://www.parker51.com/PenCaps.11.html

http://www.penlovers.com/index.cfm?t=collections&s=parker51