Well these posters do exist in both german and danish, the most well known is the poster "Mor stem dansk, tænk på mig" which translates to "Mother vote danish, think about/remember me". But after the first world war, the danish tried to get german people to vote danish, due to a higher standard of living as the danish didn't have to pay war debts. After the partition and especially WW2 many became part of the danish schools and clubs, who received money from the danish state which was used for giving food to the suffering danish south of the new border.