looking for vintage guyatone pedal schems

[small fish]

Hi guys,
I fell over a Guyatone PS-111 EQ, which seems to be quite vintage (1979 or so). I bought it for 10 euros, which will be $13 (a steal... 

Opened up and it was quite messy inside: traces were cut, I think some parts added or changed, aso. After all, it sounds quite nice, but I would really be interested in the original schematic, just to compare what they did to this pedal.
Anyone got a clue, where to find the schematics? I searched the usual places, like freeinfosociety, diystompboxes, FSB, and others but had no luck at all.

Any help will be highly appreciated 

thx guys & regards
Carsten