The officers models were built for accuracy for bullseye and other target competitions. They werecompeting against Smith&Wesson Target masterpiece models for customers. The replacement rear and front sight is very common on guns that were shot in competition as the Colt sights on the .38 models were known for loosening up which destroys accuracy. I have a .22lr model from 1937 which has the checkering, and a 1951 Officers model special .38 with a heavy barrel. The .38 had the front and rear sights replaced.
Here is a picture of my 1949 S&W .38 Target Masterpiece and my 1951 Officers Model Special.
The OMS came with the original plastic Coltwood grips. Most owners replaced them with custom target grips, mine is wearing Hogue wood grips: