Thousands of MD421s mourn their inventor: Fritz Sennheiser passed away shortly after his 98th birthday.
http://www.sennheiser.com/sennheiser/home_en.nsf/root/press_releases_180510_prof_dr_fritz_sennheiser
http://www.sennheiser.com/sennheiser/home_en.nsf/root/press_releases_180510_biographie
http://www.sennheiser.com/sennheiser/home_en.nsf/root/press_releases_180510_prof_dr_fritz_sennheiser
http://www.sennheiser.com/sennheiser/home_en.nsf/root/press_releases_180510_biographie