The A1200 doesn't have a clock battery built-in. Several different styles of expansion exist to add one. Most mount in the trapdoor slot. It's as easy as popping the cover and checking the board (assuming you have one). Most are coin cell style (which don't leak). The other way of adding a battery to an A1200 is via the clockport header on the motherboard. Obviously examining this location will require opening the machine up. AFAIK the only type ever made for this header used coin cell batteries.
