The concurrent dash numbers are interesting, and confusing to some people.
On many of the fixed sight guns, like the Model 10, there were almost always concurrent dash numbers that indicated the type of barrel that was installed (tapered or heavy). This did not seem to happen on the target sight models.
And some models show a dash change when the pinned barrel went away, but most did not.
I'm sure S&W had reasons for this, but I don't know that anyone really knows what they were.
JP

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Jack
SWCA #2475, SWHF #318