A lot of ord. rifles were modified to make them into official Army salute guns. The cast steel cone stand weighs about 1000 lbs. and was made for them. The breech was a sliding wedge, with slow screw closure, Hotchkiss type. The only thing you would be able to find out history-wise would be which Army post the piece was at when the conversion was done. There were a few that did these such as Rock Island, and often that's recorded in the records in Nat. Archives. No other history has been found on Army field cannons. The "gun books" were discarded long ago, sadly not one preserved that I know of.
The salute gun version took a Navy 6-pounder blank cartridge, centerfire. If you look inside the chamber is smaller than the bore to hold that particular cartridge.