16×2 LCD screen, blue (427 nm) and green (574 nm) LED intensity adjustment pots, LCD contrast pot, Absorption Sample, and Blank Sample buttons. A ribbon cable connects the LED and Light Sensor boards (not shown in the photo).
The cover is flipped over – orientation – top is bottom of photo – note three empty top pins – the six wired pins can be traced with a effort effort. Note giant 1k resistor.
The intensity adjustment pots set the blank readings separately for green (G) and blue (B). These should be in the 600 to 900 range.
Ribbon cable key:
LED board: — leds cathodes are tied to a common negative ground
Green blue led
Blue green led (why ?)