Hägar The Horrible - Original art for the Incentive Book sent out to publishers and created for the launch of the strip in 1973 by King Features Syndicate - page 1

To the best of my knowledge, this is the earliest known published Hägar piece out in the open.
It was made for the King Features Syndicate booklet sent out to publishers to promote Dik Browne's new strip (in 1973).
The book (containing the first ever Hägar material) and the first Hägar book ever, contains some info on Dik Browne (then famous for his work with Mort Walker on Hi and Lois) and an overviex of 3 weeks wortjs of strips (from the 4th of February 1973 onward).