Another Roman numeral mistake: The final card shows a copyright date of "MCMXV" - that's 1915. It should be MCMXCV for 1995.
Margaret's letter to Lionel is forwarded from his previous address to his and Jean's house. He doesn't give her the correct address, nor does he expect to see her again. Yet in the final scene, she calls on them as if she already knows where to go.