The -1 mod number was the change to the J frame in April 1961 at #712954. In 1970 the factory changed the serial numbering system on these guns to using an H serial number prefix at serial #826977. The mod 30 could be bought in a barrel length of 2", 3", and 4". An interesting side note; the mod 30 is a round butt gun and the mod 31 is a square butt gun. This is the only guns that S&W made a model change for the butt configuration with the same caliber and/or barrel length!
jcelect SWCA#723