This is a 21 Jewel, Special Railway, Two Tone, Hunter Movement, [HT4L-A], c.1900, in a J. Boss, 20 yr., Gold Filled Case. 

Currently mounted in a Open Face Case these are often called "Sidewinders" The above shows the Chipped & Hair-lined Dial I got it with it [one of the chips is hidden under the Hour Hand]. 

           Nice "Circle" Gold Damasking & Gilt Screws [this picture doesn't do it justice]. 

This pic. taken after Old Dial was replaced by the Montgomery Dial. 

I considered this Mint, SS, 24 hr., Canadian Dial as a replacement but wound up settling  on the Montgomery Style.

Even though Montgomery Dials didn't come in till 1904, I keep seeing many of them on pre-1904 movements. Obviously the owners had them added when they became available. So, it wouldn't be out of character to install this one on a 1900 Model 4, like this [perhaps I can install the Canadian Dial on my Menlo Park Hunter that's currently in the Aluminium Dueber Case, w/ a totally incorrect dial on it. This has the added advantage of having the Single Sunk Dial on the 17J & the Double Sunk on the 21J which was the usually Hampden configuration]. 

Inside of Case marked Keystone w/ the "Scales" Logo & J.Boss, Guaranteed 20 yr's.. This case is a bit beat up & doesn't seat well but, with a bit of effort, it gets nearly flush.  After switching Dials I believe I'll leave the Movement in this Case or perhaps another 'Hinged' Open Face Case. It makes some sense to make a Hunter Style, Railway Watch into a "Sidewinder" [easier to read while on the job]. Kind of a Transitional Step before only the Open Face Watches were "Approved" & the Hunter's "Refused" by all but the smallest Railway Companies.