Waterman 454 (sterling on BHR 54 ) in pattern possibly called Moderne or Modern or something, but known to collectors widely as "Night and Day". Considered a "better" pattern, it doesn't turn up so often, even at pen shows. All I've seen are 54 size, so I'm not sure the overall more prevalent (in silver) 452 was done in this pattern.
This set is in quite nice shape. I did not tamper with the patina.
http://vacumania.com/penteech2/waterman454nightandday.jpg
david