The number places it in the production era after the magnum cylinders were being added to the Single-Sixes. So, as you already know, your gun is a FIXED sighted gun, and that makes it a 'Old Model Single-Six Convertible.' It's not marked 'magnum' or it would have a different serial number block.
MUCH better than any other resource for us. You can join RENE, and Chad (chet15) has a Reference Guide that is INVALUABLE to collectors.
As FM alludes to, we use the RENE Reference Guide for information.
