I seem to recall reading some where that Many of the 3 inch ordnance rifles were converted to salute guns. I believe Matt Switliks 3 inch Ordnance rifle is a salute gun converted back to ML.
Correct. Something like 200 of them were converted.
Field artillery weapons of the Civil War
I asked about them here a few years ago, I think in Sept. of 2009. I saw one at the local American Legion Post (poster for a pancake breakfast said "look for the cannon" - how could I resist?).
They allowed me to scrape away the paint that made the SN unreadable. Phoenix Iron, #334, TTSL, 1863, 819#. I contacted the guy who keeps the Register asking about it, got back a "Thanks! That one wasn't in the Register!"