The Parker 15 was introduced as an inexpensive pen in 1983 and continued in production until around 2000.  The barrel has no imprint. The brushed steel slip cap has a chrome plated 'arrow' clip retained by a flat black stud. The cap is stamped around the lip "PARKER   MADE IN U.K.  PC".   This example is fitted with a cartridge converter (or "Refillable Ink Cartridge" as Parker calls them). This means that you can fill the pen as a conventional pen using ink from a bottle, but this can be easily removed (when empty!) and a cartridge fitted.   

It is fitted with a smooth-writing medium steel nib, stamped simply "PARKER".