What year is this /6 ?

What's the Numbers and letters near where it is stamped 225? Also Slant six dan posted a reply to someone a while back with the same block stampings. he told them it came from a 1980 passenger car. They also had the numbers 225 with a R822 which meant it was built 22nd August.
Hope that helps.
What the numbers and letters beside the stamping 225?