The Spencer is a short fitted jacket, without basque, only going down to mid-back, with long sleeves.
It’s origin is attributed to an English lord, George Spencer, who allegedly burned his coat by warming himself too close to the fireplace.
The Sleeve puffs is sleeve supports, special pads on the sleeves to keep in shape. They gained popularity in 1820’s-1840’s. The pads were made of cotton or linen, stuffed with cotton wool, goose feathers or down.
Fashion accessory is a wardrobe detail, without which it is impossible to imagine of the era. Some accessories were practical, others covered up the flaws or simply made the outfit “decent”, and still others were just beautiful knick-knacks.