Not Part of My Collection but I thought I'd add this "Last of the 17 Jewel, 18 size, John C. Dueber's" which were made with alternating serial Numbers along with the 21 Jewels {this one is Serial # 2527240}. The NAWCC Data Base has the 17J as One Run of 400 which only confuses the situation more {were they counted along w/ the 21J's or separately? Does this mean there were 800 17 & 21 Jewel models made, altogether? Or, 400 of each? Or 200 of each? & is your head hurting by now?}. 

This one has the Usual Spade Hour & Whip Minute Hands.

It has different Damasking than the 21 Jewel & I don't know if it has Ruby or Sapphire Pallet Stones & Steel or Brass Escape Wheel. It does have the Gold Screw-Set Jewels though.  

The Dials seem to be Identical. Another Double Sunk, Arabic Script, Dial w/ Red Marginal Figures.

This one's housed in a B&B, "Royal", 20 yr. Gold Filled Case, which is Engine Turned w/ an Engraved "Shield" Back, which has been monogrammed. No matter if there are 400 ea. or 200 ea. of these 17 & 21 Jewel John C. Dueber, ON3L-5P DR's ever made, they're damn rare now & I've only documented this one 17J & the one 21J {the one in my collection} since I started following Dueber-Hampden's 5 Yrs. ago.