OMR,

If you pull the barrel of the gun, you will likely find a date code on the underside. FWIW, my 1903 model M/S, serial #14037, was made in 1919.

There are several sources of ammunition for the gun - google is your friend here. Modern stuff can be bought via outlets like Buffalo Arms (www.buffaloarms.com. A search on gunbroker.com, gunsinternational.com, or gunsamerica.com will also turn up some options for you.

Good luck,

Ken