Looks like an early 1960's Model 39 to me,
If you focus on the slide serrations you will note they are a bit further fwd than on the Pre Model 39 below,
The nickel one above also has the new long tang and relieved left side panel that are absent below.

(Pre 39's also have the short safety lever for comparison)

Hard to tell from the pics but I would bet the OP's gun was refinished sometime in its life.



Forgot to mention the OP's gun also has the frame grooves for a dust cover where Pre 39's do not

Here is nickel 39 form the web, notice the extractor is blue not nickel although IIRC early ones are found either way