1908 Sears, Roebuck has a page devoted to the RR watches that they have for sale.
The recommended case is "Alaska metal" (some advs. call it silveroid, there are other names). All of the watches are size 18 (they note that a few RR's accept 16 size).
The case is the "cup," the movement fitted into a "swing ring" which holds the movement and fits into the cup, and the bezel with crystal which screws into the cup.
RR Accepted movements and price in the basic case and 20 year gold-fill:
21j John Hancock Hampden- $18.00, 22.35
21j Special Railway Hampden- $19.50, 23.85
23j New Railway Hampden- $21.75, 24.50
19j B. W. Raymond Elgin- $24.75, 29.10
21j Father Time Elgin- $26.75, 31.10
23j Special Railway Hampden- $27.00, 31.35
21j Veritas Elgin- $30.75, 35.10
23j Veritas Elgin- $35.75, 40.10

The same movements are also priced in Hunter, solid gold, and various fancy cases for other than RR use.
I have a 21j Spec. Railway Hampden, a nice watch.

Other catalogues will have prices for RR accepted South Bend, Howard, Waltham and other makes, but the above gives a fair idea of price range.

Wound up my grandmother's South Bend 15j half-hunter today. A nice watch with the pin that permits it to be worn on a blouse, dress, etc.