Canadian-made Sterling Silver caps with chrome plated clips, lined pattern with chevron band.  This combination of Sterling Silver with the plain arrow clip was only available in canadian production, around 1947-1948 for the vacumatic pens.  These caps all had a rhodium plating to prevent tarnish.  The finish did not stand up to wear too well, often wearing inconsistantly, and can sometimes be found with an uneven, unattractive appearance.  In addition, the soft metal is very prone to dents and dings, and finding caps in perfect condition is very hard.   Less Common Cap

Rolled Gold Cap with gold filled clip.  English made, ca. 1949.  Pattern is groups of 4 lines and a wide space, all around the cap, with a wide cap band with "Parker" in the front and "51" and gold content on the back.  Note the unique shape of the clip, common on english "51"s of the era. Less Common Cap

Parker Aerometric Full Sized Lustroloy (stainless steel) cap with chrome plated clip.  These caps had a matte finish with a thin shiny cap band when new.  Finish was more "brushed" than the earlier vacumatic series caps.  The finish did not stand up to wear too well and quickly wore off.  Available in both full and demi sizes.  Common Cap

Parker Aerometric Full sized and Demi sized Lustroloy (stainless steel) caps with gold filled clips.  These caps had a matte finish with a thin shiny cap band when new.  Finish was more less "brushed" than the earlier vacumatic series caps.  The finish did not stand up to wear too well and quickly wore off.  Available in both full and demi sizes.  Common Caps