Much better images and, unfortunately, confirms what my eyes were seeing ~ if you care, DO NOT power this board up again ~ it needs repair/revamp/reworking first...
...green crusties in the keyboard IC socket gave it away... all of that area will need redressing (new IC socket, check all components/traces, replace all the tantalum caps...
...the green line defines the approx. area of visible concern ... the fact the ICs between the ISA slots are contaminated, means the fluid when under the 1st ISA slot to get there. It looks like wash marks (lets hope it wasn't vinegar), but unfortunately this extends to the PLCC socket (replace it), plus any other glue logic there-abouts...I marked some tants near power connector..all caps of this type on the board should be replaced (before they forego their self healing properties and embrace the freedom of self explosive sacrifice =)....I marked the small crystal can ... the portion closest the the edge of PCB is alkaline creep damage...inside the soldered earth strap can is fine ... as it does, the creep has working it's way around the periphery of the PCB...there may be more damage solder side... underneath the keyboard controller IC is guaranteed to be a horrorshow.... =^/
edit: and those DIL switch blocks can't be trusted anymore...