I got an Amiga 1200 off ebay and it works great, board looks perfect, no leakage, no bad traces, nothing, and yet I have this mysterious mod I've never seen before. Does anyone know what it is?
I believe it is to clean the weak CCK clock signal coming from Alice to Budgie.
PCB rev 1.d4 and 2b should have this.
It is on the R2 schematic (http://www.amigawiki.de/dnl/schematics/A1200_R2.pdf) - search for "BUDGIE BLUES" and check pin 36 (CCK).
I think U37 ("TI 231 JFA HC08" in your photo) is a quad positive-or (74F32 / SN74S32) which is serving as the buffer.