As best as I can tell from your pictures it looks like a Waterman's Chased Overlay with the old straight cap design, maybe a 0504. Could be a 0502, but the nib looks a little larger to me. This would be from the early 1900's. If it is a true Waterman, the quality of construction should be very good - and that's hard to tell without holding the pen in hand. There were a lot of cheap overlays similar to this made, but you usually can detect seams in the overlay and that sort of thing indicating cheap construction.
It would help to see the feed. It should be the typical Waterman spoon feed from 1899, or the earlier 3 fissure feed.
Edited by Procyon, 05 April 2012 - 05:31 PM.