This is an original No 21C Winchester front sight for Models 1873, 1886, 1892, and 1892 barrels that are 20" or under (aka carbine sizes). These ORIGINAL front sights are largely from Winchester Sporting rifles produced in the late 1800 to early 1900s. The sights have a high middle center blade that is .381 inches high. The sight fits into the 3/8 inch dovetail on the Winchester barrel top dovetail.
