Your clients floor is probably a prefinished product. If it is the milky clear on it is actually a 2 part oil/wax product that is recently new to the market. I hate it and it scratches easy. Basically you add part A and part B together like an epoxy. Apply with a steel trowel, and wait until hard and buff with a white pad on an Orbital floor buffer.
The picture provided is the same "prefinished" floor. I used a white oak unfinished tread which seemed more red. I used Natural Peach water-based stain from Minwax, I did alter it with gold and brown pigments to achieve the milky color and to cancel the red from the oak. Light hand sanded it with 320 grit and added 3 coats of the Bona Natural. I always use 3 coats of anything. But it says 2. You will be pleasantly pleased with that clear. You might beable to get by without the stain, I used it to soften the redish tint on some of the treads.