23 jewel Illinois "Sangamo Special" railroad watch. Serviced

Here we have a "23" jewel Illinois Sangamo Special railroad watch made by the Illinois Watch Co in1916.
I myself wonder if the 23 jewel claim with Jeweled Barrel was simply a marketing ploy by the makers as having stripped and serviced the watch there is no trace of any jewels within or around the spring barrel and no facility or possibility of fitting any jewels. As far as I can be certain everything within this movement is correct and is original and it is identical to other watches from the same run. Different production runs feature an obvious upper barrel jewel and also differ in the engraved claims on the movement. A strange anomaly for this model but I confirm there are in fact just 21 jewels. This run of Sangamo's had a total production of 8070 examples.
It is in fact a very high grade movement with 21 jewels a fully capped Swiss lever escapement with double roller, gold timing screws and  a sprung micro-regulator. The movement features Gold (alloy) train wheels with a steel escape wheel and raised Gold jewel settings. The movement is beautifully finished with a lovely damaskeened pattern to the plates and inlaid engraved script.
This watch has just had a full service so it's running very nicely and is keeping excellent good time.
The watch is stem wind and lever set (Withdraw the small lever by the 1 and rotate the crown to set the time) winding and setting both working smoothly.
The watch is housed in a 3 piece Chrome or Nickel plated base metal display case with screw on/off covers front and rear with mineral glass crystals front and rear.
The case is in lovely condition and both covers remove and replace easily and both screw down square and tight.
Double sunk white enamel dial is in lovely condition, there is a small chip at the top of the sub seconds dial at the join with the main part of the dial.
A very good set of spade style hands.
Overall a lovely watch working well and perhaps a bit of an enigma, one for the collector!