That serial number should make it 1926. Very nice looking gun.
I have a couple of '20s-era M&Ps, and I shoot 148 grain wadcutter match ammo in them. These are loaded for accuracy, not power, and you can shoot them without worrying about whether you are stressing an older frame and barrel. To be realistic, you could probably shoot any standard pressure modern .38 Special round, but I would avoid +P loads and the zippier standard loads. These older guns deserve to loaf a bit on their outings to the range.
ADDENDUM: Here's a thread I bet you'd like to browse in.
http://smith-wessonforum.com/s-w-ha...8906-show-off-your-m-p-revolvers-pre-10s.html