According to the SCSW : 927 steel frame guns were made first but not assembled or sold until 1966 ,
They serial in the 39000 range and 60000 - 64000 and again 81000 to 82000.

The first guns sold were alloy pre 39's beginning with serial 1001 to 2600,
Early guns are different and have smaller safety levers, a short tang, long extractor, unique frame backstrap,
no cutout on left grip panel needed for the safety lever , no trigger play spring and no model stamping.

"what exactly do they mean by shorter tang? I dont quite understand what that means.

The "TANG" sticks out just above the web of your hand and protects it from the slide and hammer .