Welcome to the forum.
There's not much more to tell if you have the letter. Roy provides a nice little summary.
The Model 1903, the 2nd Model, has quite a few changes and looks a bit different:
.32 Hand Ejector 2nd Model (Model of 1903)
There were 3 screw and 4 screw side plates with no relation to the vintage of the guns, see this thread:
pictures of HE
And there were two hammer spur lengths. Also there were target versions that are rare:
32 Hand Ejector 1st Model -Target (Model 1896)