The 1881H SSNs is certainly a minor variety in the great scheme of things. My guess is it's from a partially-used 1876H obverse that was carried over.
That being said, it is an easily-recognizable variety, is listed in the standard catalogs and is well known to be really scarce -- all positives. So there are going to be people who want one badly and will pay up for one. How much is hard to say, but in my opinion two determined bidders could easily push your coin north of $1000. It's most unlikely that a hoard of them will ever turn up! And yours is a pretty nice one.