This is a question of the huge knowledge base here, that amazes me quite frequently. I recently added a model 19-4 to my rather modest collection, the features, are what draws my question. I have seen the majority of 4" specimens with black on black sights, and almost a semi target?, trigger a and hammer. Mine has a wide target trigger, and hammer, and a red insert front sight, with white outline rear. Are these features a special order on the k frames? They appear to be standard on n frames. In my limited research the model 15 shows even less occasion of the mentioned features. Thank you in advance for the input, attempting to build the knowledge