OPUS 88 Shell Fountain Pen (Cartridge/Converter) - Mother of Pearl - Medium NibOPUS 88 shell Fountain pen. OPUS 88 have been making shell pens for over 20 years and have a reputation of producing the the highest quality pens by using New Zealand and Australian shell. This is a largish pen and can be used posted or unposted. For posting, the cap can be scewed onto the barrel section. This OPUS 88 pen is a cartridge converter pen and is supplied with a Schmidt converter. Details: Dimensions: 140mm x 16mm capped, 123mm uncapped,