Peter: you should have a 'F' (lowest) grade hammer gun made in 1903. Please check the FAQs for sources of reproduction buttplates. The good news is that there are some excellent LC smiths in Wisconsin. Be aware however that the cost of returning your gun to a functional condition may very well exceed it's value, esp. if parts must be replaced or fabricated.
Hugh Lomas 920-876-3745 Elkhart Lake, WI.
Pete Day Rhinelander, WI 715-362-3402
Dennis Potter Muskego, WI 414-425-4830 potter@execpc.com