A martingale is a part of a horse's tack. This is a standing martingale, having been attached to one ond of the noseband and at the other end to the horse's girth. The martingale helps control the horse's head carriage, preventing him or her from raising the head too high. There is evidence that the martingale may have been used as early as the Assyrian Empire, most likely Mid-Assyrian c1352-1050 BCE.
Ours is a fancy, attractive martingale and it dates to the 19thC. Made of good leather, now rather dry, with a potential crease just past the middle, above the bottom brass and porcelain medallion. A nice moisturizing polish would be beneficial. The entire perimeter of the martingale is decoratively cut into small scallops, each one defined with a stylized Van Dyke sharply indented edge. The brass buckle and medallion are solid. The porcelain half-ball is decorated with a brass insert at center. The porcelain shows an attractive crackle that is not at all threatening. There looks like there might be about a 1 inch piece of missing loop at the very center, through which a part of the tack strapping might have been threaded. But it also could have been designed that way. Hard to really tell, due to its advanced age. A shade under 10" long, with the attachment loop at top adding another inch. 4" wide at its widest point at the bottom.