The large silver medallions were used for K-frame grips only during very early production, ca. 1930. I think there are some which can pin down the use date more closely, but suffice it to say that K-frame large silver medallion grips were never plentiful. I am not sure what the large medallion stocks you describe fit. Sometimes N-frame grips can be forced onto a K-frame, but they do not fit well. Can you post a picture?