Confusion may arise when not all letters are present such as (documented) S10874 a Specialty and S13576 an Eagle and the above 223S Specialty
The next level of confusion arises when considering the 140 SBTs made by Marlin between 1946 and 1950. Among my notes I show that the serial numbers of these 140 guns are preceded by the letter S but I have not personally documented any gun made later than 1944. Perhaps some one who owns one of these guns can chime in with a serial number for an Olympic grade with serial number in the 1-56800 range. (The problem with this is that there were Olympics made in the 1920's and 30's in the same serial number range.) However, the S prefix of the Marlin SBT could mean that they were made by Marlin which renders it ambiguous.
Now, it's all clear, right?