There's a small auction company in a small town nowhere near where I live that allows online proxy bids; its a bit of a gamble, because you only have a couple of pictures to go by, but I've gotten lucky with them before. Today's gamble arrived, and was somewhat better then I expected. It'll be awhile before I have the time and nerve to disassemble it, but here's what I know so far.
Hallmarks appear to be London, 1863. Maker is "PW", which I can't find a match for (at least not for 1863 London). The makers stamp is very plain (just two letters, no shield or anything). The dial also appears to be silver; the numbers are attached separately, and it appears to be hand engraved (which I imagine was common). The case back sports a subtle design that at a second glance seems far more interesting then at first; not sure what to make of it.
The movement is unsigned but numbered, and appears to be a fusee driven English lever (straight teeth on the escape wheel). Only the balance and escape wheel seem to be jeweled. Fusee chain and balance staff appear intact. All in all, a nice mid-grade English lever. Probably won't know more until I take it apart, but as ever, I would welcome any additional insight.