Dish's model number system is quite logical. The first two digits indicate the receiver model, so a 4722 system includes a 4700 receiver. The last two digits in the system model number describes the additional antenna system components.

xx00 = Receiver only.
xx10 = Receiver with Dish300 and 1 single LNB (a discontinued package).
xx12 = Receiver with Dish500, 2 single LNBs and an SW21.
xx20 = Receiver with Dish300 and 1 dual LNB.
xx22 = Receiver with Dish500, 2 dual LNBs and an SW42 (or 2 SW21s).
xx22T = Receiver with Dish500, and the new Twin LNB
xx23 = Receiver with Dish500 Twin, Dish300, 2 SW21s.
6023UQ = 6000 receiver or kit including an 8PSK High Def TV module (U), also Dish500 Twin, Dish300, 2 SW21s (Q).

DishPro line
xxx-22A = Receiver with Dish500, 2 dual LNBs and 2 SW21s.
xxx-22B = Receiver with Dish500 and Twin LNB.
xxx-22D = Receiver with Dish500 and DishPro Twin LNB.