Dres. is short for the Latin "Doctores"

Dres. is short for the Latin "Doctores" and as such is used when two or more persons holding the aforementioned title are adressed in a German letter head or appear on a shingle:

Dres. Limbach & Roundtree
Rechtsanwälte

Gisela Strauss
Tech Translator in the greater Munich area
& virtually, everywhere.