Hi Rick,
Your gun was made in 1923. The Nitro Special was a "hardware store gun" built for the masses. However, NS's are generally held in higher esteem then similar hardware store guns made during that period. If it were mine, I'd shoot standard, or lighter, 2.75 field loads in it. Also those old NS's had a lot of drop at the heal, if you're used to shooting modern shotguns you'll have to adjust your shooting style or expect to shoot under your target. Check out this article I wrote a few years ago it explains it better
http://www.fourten.org.uk/st_patterning.html . One last thing, there should be a small number, 1 through 4, located on the barrel flats. This number is the choke on the barrel, 4 represents full choke and I believe 1 (or maybe 0) represents cylinder. Skeetx gave you the value.
Good luck with your Nitro Special.
Steve
BTW foul = icky, fowl = bird
