I was told by the fellow who sold it, that the machine was used more-or-less daily for a family of 5 and I believe he said it was 8 or 9 years old. I doubt it ever saw a citric-acid wash cycle.
As for the cleaner, I started with plain white vinegar when the spider was still attached to the drum and switched to diluted CLR on the spider. Anything more acidic than vinegar will make a mess of cheaper stainless in my experience. I followed with a dilute ammonia wash.
The scaling, was most certinaly lime with whatever detergent salts wanted to linger. Lake Ontario water is considered 'moderate' in terms of water hardness and city water averages at 120 milligram/litre or 8.4 grains/imperial gallon.
The sink is a 21" wide. The inner drum is 19 1/2" in diameter. The outer drum is 22" (top-bottom) and 21" (wide). The W1918/W1903 are the Miele 5kg series, and have a frame width of about 23 1/2".