Howdy Colton,
I assume you are asking about what Cimarron calls Old Model and Pre-War versions of the Model P. The Old Model is how Colt made the guns up until the mid 1890's. It uses a setscrew in the front of the frame to secure the cylinder pin, and the head on the ejector is round, called a bullseye ejector. Some folks call this the black powder frame (although in modern reproductions, smokeless powder is fine). The Pre-War version is how Colt made the 1st Generation SAA from mid-1890's until World War 2 This frame uses a spring-loaded transverse push-button to secure the cylinder pin, and the ejector head is a crescent shape. Also, current Pre-War models from Cimarron have a medallion on the wood grips, and the Old Model guns have no medallions. Otherwise the guns are identical. Sights are identical, with a v-shaped rear and tapered front. They both have coil hand spring. There are "non-authentic" versions available which have squared front and rear sights, such as the stainless guns and the Evil Roy model plus the ER has an action job.