They are freq dependent. The daughter boards on the modules are the freq dependent parts. The daughter boards are the little approx 1x4in circuit boards with a few caps & other components. Check the numbers on the daughter board to see if they are the same. If not swap the daughter boards. As I recall, there about 3 or 4 "bands" that they fall into.
I recall that the A & E modules can be differentiated by the number of horizontal lines on the front of the module. IIRC, the A has 7 horizontal lines and the E has 9. Again, IIRC, the E version is HD capable and although they will plug into the same backplane, are not compatible.