I wouldn't say the number/hierarchy system is that complicated once you get more familiar with it. As mentioned above, the first number is mostly what tells you where the machine falls on the line (bottom, middle, top) and the other two are the series of the machine. Starting with the late 50s/early 60s, the top of line model was the A900, then changed to the A902 (as according to the whole series). Then with the 06 series (first iteration of the "New Generation machines, from 1966-74), the 906 was the top. Then for the 07/08 series (the later iteration from 75-80), the 908 was top. The very top machines have entirely pushbutton controls rather than a dial. However, the most sought-after models are the 800 series, which are one step down from the top and still have the dial. My machines are an A107 (1975) and A506 (1985). The 107 is, as you may expect, a very basic single-speed, small tub machine. It's one model up from the bottom; the bottom was the 106, only difference is the 107 has the delicated cycle and the 106 does not. The 506, contrary to its name, was actually produced during the run of the 12-series (1984-90), and is pretty much exactly in the middle of the hierarchy. It is single-speed with delicate as well, but large tub. So yeah, that's how you can determine based on the model number where the machine falls on the line (and in most cases, what line it belongs to).