In the original American editions, the name change, from National Periodical Comics to DC Comics, occurred in December 1976 (for March 1977 cover-dated comics).
My theory is that there would have been some delay for foreign editions like KG Murray before the name change took effect. So in all likelihood, the first KG Murray edition to have a 'copyright DC Comics' notice in it is the first edition of that title for 1977.