Nick,firstly you'll have to establish how the floor was finished and maintained.Then find a supplier for Bonakemi products,they will advise you on the correct method.
I hazard a guess,the floor was either lacquered or oiled, Bonakemi has products to maintain, clean or refinish both types of sealing.
If you'r considering expanding this line of work,far more profitable than carpetcleaning btw,I recommend taking the Bonakemi classes,top people.
David