The case appears to be very similar to some cases used by Silas Hoadley and other tall clock makers. Hoadley, if I recall correctly, had his cases manufactured for him (as did others) so this may be a similar situation. This case has the same basic proportions and trimwork of cases from Hoadley's era. The crown is different from others I have seen but that could just be a makers specification. In any event the case appears to be similar to cases I've seen dating from the early 1800's rather than late 1700's. The arched face is what gives me this impression as earlier faces tended to be square in my observations. The metal dial face and lack of a moon dial says to me that it is in the earlier 1800's. I'd think probably before, say, 1820. The fact that the dial is metal rather than wood could mean it's more likely made post 1800. Better pictures of the case trimwork, feet, movement, and other details may also help date the timeframe.