This fine hat has not seen the light of day in over 12+ years and just came out of a large collection in Louisiana. It is a regulation US M1858 Hardee pattern hat with original insignia and fasteners (as shown). It is in near fine condition other than for an old stress crack on the upper side left crown (see photo) and the original paper tag inside the crown is near flawless.
This hat is adorned with original US Engineer insignia, a jaunty ostrich plume, a yellow-gold cavalry/dragoon hat cord and the company letter A. It likely was worn by a member of Company A, US Engineers, circa 1862-1864. You can read about the unit here: https://armyhistory.org/company-a-u-s-engineer-battalion-june-1864-one-of-the-most-brilliant-scenes-of-the-war/ (cut and paste the link in your browser window).
On a one to ten scale, this fine piece of headgear is a solid 8+ and would be the centerpiece in any Civil War collection. It is not unusual to see hat cords for artillery, infantry and cavalry as members of the US Engineers were pulled from a wide array of existing units. Company A retained approximately 150 or less men by 1864. This one is pure museum or investment grade all the way!