Nice early 39-2 , there is an interesting evolutuion of its design begnning in 1955 as "The 9mm auto" (AKA Pre 39) since it was S&W's only 9mm handgun at the time.

When S&W went to model numbers it became the Model 39, the extractor was improved due to breakage in the old design right around the time your gun was made and introduced as the 39-2 , there was also a 14 shot version introduced around that time as well as the Model 59.

Neat gun, enjoy...PS are you still on the job ?