Anachronisms: Father Collins wears a traditional black garment with white "dog collar" but apparently in the period this film was set, the law forbad a catholic priest to dress this way.
Anachronisms: As he is driving Major Doryan to the camp, the corporal asks him if he had been in the Second Battle of the Marne. The Second Battle of the Marne was fought in July and August of 1918 near the end of WWI while events in Ryan's Daughter are set in 1916 not long after the Easter Rising.