Here's a picture of a Treadwell wrought iron and steel 6-pounder gun. It is unmarked as far as I can tell, but all of the characteristics and measurements match exactly with the descriptions in various original documents.
The Treadwell 6-pounders had the same measurements as the US M1841 bronze field gun, with the exception of the screwed-on trunnion band. The one pictured has a raised vent, as if the vent bushing had not been screwed in all the way, or Treadwell had made some change in this area, for which we have found no documentation.
Basically Daniel Treadwell was a very successful inventor in the early 19th C. He made a fortune from his inventions of textile machinery. He then had an idea on how to make a stronger non-bronze cannon, and invested hundereds of $K in a huge machine to compress welding-heat wrought iron onto steel to make cannons. He sold a few 32-pounder "wrought iron and steel" guns to the Navy, which survive in Washington DC and Norfolk VA.
He sold eight? 6-pounder field guns built on his plan, to the Army for testing. Until now, none were thought to have survived. The Army tested them to extremity, and the results are well documented in the National Archives, RG156 as I recall. They did quite well but the Army was not sold on his pattern of cannons.
I made this information available to a distinguished late individual I knew who was a published author, but it never got into print. I thought I should at least post it somewhere in case my stuff goes to the junk man after I check out (which hopefully will not be too soon.)
I also sent it to Jim Bender of OH, who is the new "keeper of the register" of surviving US Civil War era artillery.
