I have two 7A18, a 7A18A and a 7A18(Option 6). I don't have a 7A18N (and wouldn't really want one). As far as I am aware 7A18 and 7A18A are significantly different in their circuitry and even have different Service Manuals. The "N" designation indicates that there is no readout including the "Identify" function. Since I have never seen a 7A18N, I don't know what the situation regarding the "Position" and "Identify" controls might be.

Neither of my Service Manuals list an Option 1, neither does TekWiki. The entry in Tekwiki shows a main photograph of a 7A18A, but labels it as a 7A18. It also states that the 7A26 and 7A24 share the same front panel as the 7A18, which isn't totally correct, as the 7A26 has a second slide-switch to change the bandwidth between "FULL" and "20MHz" and the 7A24 labels the inputs as 50 Ohm and the "VOLTS/DIV" switches have reduced ranges (8 positions from 1VOLT/DIV to 5mV/DIV, where the other plugins have 10 positions from 5VOLT/DIV to 5mV DIV).

Option 6 is the offset function, which replaces the "Identify" buttons with ten-turn pots and adds a fourth position for the "AC/GND/DC" switch, i.e. "DC OFFSET".

Perhaps if someone has a 7A18N, or a 7A18 (Option 1) and could post some photographs, it might be informative.

Colin.