This watch looks very much like an early P.S. Bartlett Model 57 with under sprung steel balance, hidden stud and engraved index; except it has 4mm translucent jewels in real jewel settings secured with 3 screws. It has the standard M57 train, 3-arm blunt-end escape wheel and enclosed English style pallet. It has a cantilevered potance (holds bottom arbor of balance) but has different shape than the standard factory part #215. The regulator looks identical to the standard part. A couple obvious differences: it has 13 jewels instead of 15 (the pallet arbor is not jeweled), and the case screw passes through the top plate and screws into the pillar plate (a late M57 feature). The top plate does not encircle the barrel (a M57 feature around S/N 30000 or so).

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The top plate and pillar plate measure 42.7mm and 45.7mm, respectively, approximately the same as the standard Model 57. As best I can determine with dividers, the position of all arbor holes and pillars measure exactly with standard Model 57. Factory dials are interchangeable (e.g., AT #27902). Pillar screws are interchangeable (at least with AT #27902). The winding arbor fits a #5 key, typical for a model 57. The length of the barrel bridge at its base (33.2mm) is consistent with Model 57 (see comparisons on the Russell #20146 page). Similarly with the balance bridge total length (30.1mm), length of head (15.3mm) and width of base (12.2mm).
	The pillar plate has the same style click, oblong ratchet bridge and long bridge. However, the comma click and spring are not the same shape as standard M57 parts. The ratchet bridge is consistent with M57 with width (10.9mm), length (18.5 and W/L ration (.589) (see comparisons on the Russell #20146 page). The long bridge measures 7.2mm wide and appears identical with the standard M57 part as best as I can determine with dividers. The pillar plate also has the standard peep holes for observing the escapement in motion. Although snug, the minute wheel fits AT #27902 with stud width of .9mm. Note the 4 & 9 numbers stamped on the pillar plate are in consistent location with M57 subassembly number; however the arrangement is vertical whereas I believe horizontal was standard. Vertical arrangement started with 3 or more digit subassembly numbers, reading bottom up (in which case if this is a subassembly number it would be 94, which is consistent with the number 4 stamped under the balance bridge and hour wheel (#5 is also on the hour wheel). The number 94 is also stamped under the top plate (4 over 9).
The gilding of the Hall movement is quite good (factory ??), but the finish of the pillars on the pillar plate is consistent with the P.S. Bartlett grade, not the AT grade.