That's early, experimental Tortoiseshell, a non standard shape in small pieces, but the tricorn attenuated bottles might have been developed from this sort of thing.
Completely consistent with having a broken pontil scar, it would have been made before they had polishing facilties readily available, I suppose.
The colours in early Tortiseshell are lovely, not boring browns but rich, deep, warm tones.

It is slightly reminiscent of a certain brand of whisky bottle, isn't it? Dimple.