It would appear that KLM used the radio operators up through the 1957 time period. I use to fly a former KLM L1049H that had the aft facing RO station right behind the Capt. seat. As I recall these aircraft were built in the 1956/57 time period. I suppose they would have seen service down in Africa as well as Indonesia. Also, these were the first aircraft I recall seeing with SELCAL installed although I do not recall whether it was HF or VHF only.