[lead]

I'm kinda guessing here, but Marlin put out a number of variations of it's model 60 over the years. Sometimes the model number indicted what the variation was. For instance the 60SS was the stainless steel version.
Is the stock walnut? It could just mean the type stock, as opposed to the standard birch stock.
Regardless, it is the same action, which is a proven work horse. Every shooter should have at least one model 60 in their collection.