For your "PN" prefix Python you will have to call the factory as it was made after 1985 (no publication goes beyond that date). They will give you the date over the phone.
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Dont you love the simple answers you get around here
Ask to date a colt and you get so many help full answers.
To date a colt is to check the cylinder tightness and finish. If it still goes bang it will out live you.
Just remember to cuddle it on saturday nights.