The #7 in rubber is known for the colored ring at top of pen, which indicates nib grade. The #7 essentially is a Waterman 55 with the traditional #5 nib replaced by a similar-sized nib with keyhole style vent hole, a nib also marked with the color to reflect the stripe on the pen. Given that #7 parts and 55 parts and caps from different color #7 pens are physically interchangeable, one can but imagine the potential for frankenpens.
This one was a quite clean #7 "Red". I'd highlighted (reversibly) the imprints for sale, and this one had nice imprints.
regards
david
