I think you're in the right ballpark with the anniversary headbadge dating it to about 1968-1970 or 1971.
Do you know about Kurt's Headbadge site expansion into the world of Raleigh ? Many catalogs online in one handy place:
Raleigh Catalog Database Archive
Carlton used those lugs on a lot of 531 bikes, including the pro, the international, and the comp, and I think even the super course for a while IIRC.