Double-ended pen

A double-ended pen comprising:

• a pair of elongated liquid-holding reservoirs each having
• a rear end, both rear ends being substantially identical,
• a front end having a liquid-applying tip,
• an intermediate portion between the ends and having at the rear end a predetermined relatively small outside diameter, and
• a snap-type retaining formation;
• an intermediate coupling sleeve centered on an axis and having a pair of axially oppositely open seats each receiving a respective one of the rear ends and provided with means for retaining the respective rear ends securely therein against axial displacement relative to the coupling sleeve, the sleeve having a pair of axially opposite ends having axially oppositely directed end surfaces each having at least one portion extending at an acute angle to a plane perpendicular to the axis, the ends being of a diameter greater than the outside diameter of the intermediate portions and projecting radially therepast when the respective rear ends are fitted in the seats;
• and
• a pair of respective caps each adapted to fit over a respective one of the reservoirs and each having
• a rear end substantially of the same diameter as the respective rear end of the sleeve and having an end surface with a surface portion complementary to the one portion of the respective sleeve end surface and engageable flush and complementarily therewith in a mounted position of the cap on the respective reservoir,
• an internal snap-type retaining formation complementary to and engaged with the snap-type retaining formation of the respective reservoir in the mounted position of the cap, whereby when one of the caps is twisted relative to the sleeve the two surface portions cam the one cap axially off the respective reservoir.