Hanomag-Henschel was taken over by Mercedes-Benz in 1970. The brand was kept for a while, but some models were also sold under the Mercedes-Benz badge. So it might be that the papers said that the manufacturer was Hanomag-Henschel, as they still were built in Hamburg-Harburg (ex-Tempo factory) and Bremen-Sebaldsbrück (ex-Borgward factory).
One more point for you.