Part of that Empire-slash-Regency-slash-Jane-Austen-inspired-outfit I made for my friend was also a Spencer. A spencer is a short, fitted jacket worn by women around 1790-1820.
The one I made was out of green manchester with a brown ribbon, cute green flower-y lining, beautiful buttons and a wide neckline.
I used parts of a spencer-pattern out of Janet Arnold’s Patterns of Fashion 1, Englishwomen’s dresses and their construction c.1660-1860, but not the whole, because it did not quite match my design. So the rest I adjusted and improvised and made my own.