This description in The Grand Sophy by Georgette Heyer makes me wonder if Georgette Heyer was looking at this 1817 Ackermann fashion plate of The Glengary Habit when she wrote the passage:
When Miss Wraxton’s invitation was conveyed to Sophy she professed herself happy to accept it and at once desired Miss Jane Storridge to press out her riding dress. This garment, when she appeared in it on the following afternoon, filled Cecilia with envy but slightly staggered her brother, who could not feel that a habit made of pale blue cloth, with epaulettes and frogs, a la Hussar, and sleeves braided halfway up the arm, would win approval from Miss Wraxton. Blue kid gloves and half-boots, a high-standing collar trimmed with lace, a muslin cravat, narrow lace ruffles at the wrists, and a tall-crowned hat, like a shako, with a peak over the eyes, and a plume of curled ostrich feathers completed this dashing toilette. The tightly fitting habit set off Sophy’s magnificent figure to admiration; and from under the brim of her hat her brown locks curled quite charmingly; but Mr. Rivenhall, appealed to by his sister to subscribe to her conviction that Sophy looked beautiful, merely bowed, and said that he was no judge of such matters.
The mannish riding attire in the above image from 1816 is simpler than the first image, lacking the epaulettes, military-style piping and frogs, but it does emulate the masculine style and echoes a military overtone with the Shako hat. It is interesting to note that until the mid-19th century tailors, not dress-makers, designed female riding habits.
The riding hat, or Shako Hat, was adapted from military headdress worn by the Infantry. By 1800, the cocked hat had been replaced by Shakos ornamented with a brass plate bearing the King’s crest. They sported a tuft fixed in front rising from a black cockade. After each war it had been the habit of the British Army to adopt a head-cover belonging to its allies or the enemy.The cylindrical, flat-topped Shako adopted for the Infantry after the Napoleonic Wars was in vogue among Britain’s Continental Allies. Feminine versions of the Shako were often tied with sheer scarves which trailed behind and had feather plumes in front.
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