All H&H accessories seem to be small run, of good quality, made by outside contractors, and only seem to be offered for a season or two. I would agree with jmc, and suggest to take it to a good watchmaker, he should be able to identify the movement, and may give you an idea who SB(?) and Co are (small writing on the face under the 6 o'clock position). He may also be able to offer an estimate of value.
Good luck!