There is a chance that the month and year of production are to be found marked inside the back of the case. I’m going to guess early 1960s.
This is my Royal ref. 7904 The serial number dates it to the mid 1950's. The exact year is hard to work out but the serial number and ref. number are both marked on the outside of the caseback on mine. Ask for a photo or just ask what's marked on the back.