That is quite a history on your 39 and it looks fantastic for so many miles. The SCSW doesn't have particular dates for pre-1970 serial numbers so an exact year is difficult. I can tell you that they were started with #1001 in 1954 and ran to #115000 by 1970 when the A prefix started.

So all things being equal and your number being about 25% into production numbers I would guess around the late 50's and depending on annual production perhaps as late as 1960...I wouldn't guess it to be much later than that.

Nice 39 you have with a great family history! Hang on to it and enjoy.