wel i got a very little info on this for you.
road king were made by eaton and were imported to Canada from Hungary.
the article i read references the name Csepel “Superla so i would look into those names as well.
they were also known as schwinn-csespal. and were produced by Schwinn until 2003 when they stopped building bikes.
the rear hub,if original should be a Granat coaster hub as these seem to be what were stock to these bikes.
im assuming yours is maybe ww2 era by the skip tooth drive line,but i cannot be sure. but the article i read states the road king was a 69 model year. so i would go with that
so that's about all i got on this bike
it appears to be a limited production with about 281,355 for the 69 year.
and all the pictures of the eaton bikes i saw were a lot like yours so i think we are on the right track here.
again im just going by reference,but hopefully it helps.
if you need a value on this one, i would say anywhere from 200-500 for the right buyer.
but again just a guess and what i would ask for such a bike in my shop.
hope my 2 cents helps
sean