St50 just purcherd to find out its 10 years newer

I have just purchered a ST50 on 29th March which was registered as a 1969, and shop had confirmation letter dating the bike as 1969
I only wanted a "69" bike, but when looking for some parts soon reallised that they did not make this model until 1979
ST50MZ Dax Chopper
not sure what to do now, as love the bike but its def not what I was after due to wanting a bike made year I was born.

also not sure how I would get date changed to 1979 and ig that would increase decrease the bikes value.

any advice would be helpfull

Pic of the bike to show model