And quite right too, but given that I have never met your friend I can only go on the basis of whatever I have read and seen about the Civil War in books and online, and it appears that the hat in question barely makes an appearance in the vast majority of published and pictorial records of the conflict, except in reference to the headgear worn by the men of the Iron Brigade.
So at that point the discussion should perhaps rest.
Not well regarded..... Bloody understatement mucker. We had the flaming things on CVR, we didn't know what or where to store the things. Got in the way inside, hang 'em outside and you sounded like Quasimodo having a good time!!!
Strange therefore that the hat hardly features among the many photographs and other pictorial representations of the Union Army of that era and furthermore that the distinguishing feature of the Iron Brigade, any time it is referenced, is their distinctive black hats, which seemed to set them apart from their comrades.
The tall, brimmed Hardee Hat was the pre-war full dress US Army hat (normally worn with a long frock coat). But due to war-austerity the vast majority of troops wore the cheap, peaked forage cap and the shorter, cheaper sack coat. However, the Iron Brigade (and some other units) held on to their full dress Hardee Hats and frock-coats as a matter of unit pride and esprit de corps (along with a few black slouch hats when they couldn't get the full rig Hardee). Union heavy artillery units also routinely wore them for some reason. So while the Iron Brigade was particularly known for its Hardee hats, they weren't unique to that brigade.
In the Western theatre of war, Union troops tended to wear slouch-hats more than forage caps, again with the odd Hardee thrown in.
It was standard issue for pre-war US army Regular units which amounted to about 18,000 men. The vast majority of Union units during the war were volunteer and militia regiments which wore a variety of headgear such as the kepi and various slouch hats.
The Iron Brigade, also known as The Black Hats, Black Hat Brigade, Iron Brigade of the West, and originally King's Wisconsin Brigade was an infantrybrigade in the UnionArmy of the Potomac during the American Civil War. Although it fought entirely in the Eastern Theater, it was composed of regiments from three Western states that are now within the region of the Midwest. Noted for its strong discipline, its unique uniform appearance and its tenacious fighting ability, the Iron Brigade suffered the highest percentage of casualties of any brigade in the war.
The uniform of the Iron brigade differed some what to the standard uniform of the Union army at the time. It was designed to be more of a dress uniform that resembled a suit rather than the more common infantry men's kit. It consisted of:
A Hardee black hat: A tall blocked, brimmed black hat, featuring a brass infantry bugle, a red Corp circle patch and brass numbers/letters of the front to indicate units and companies. A brass eagle badge on the side used to hold the brim up in a slouch, and finally an ostrich feather plume.
Union Frock coat.: A long, dark blue coat that came down to the mid thighs, resembling that of an officers coat. Fitted with a single breasted row of 9 brass buttons, each with the federal eagle on them. The cuffs and collars had light blue trimming. And 2 smaller brass buttons on the cuffs. The inside of the coat was also lined with cotton to make a better fit.
Light/dark blue trousers: depending on the period of the war and unit, trousers versed from light, sky blue to a dark blue the same colour as the coat. The trouser extended from the mid waist down to the ankles and had a pocket on either side.
White canvas gaiter: white canvas leggings with leather straps to prevent stones and dirt getting into the shoes whilst in the field.
All other equipment not mentioned is simply the standard field equipment of the Union army consisting of canteens, belts, cartridge box, Bayonet and scabbard, haversack and other various items of kit.