Hola folks....
Came across this in my shed.
I used to use it to text my LED readings, for LUX/PAR (light output).
It's a Waterproof photodiode, on an acrylic stick.
With a lengthy whip, to connect to an electrical AC/DC meter.
I don't remember what I paid for any of it, but...
As a replacement waterproof photodiode is upwards of $80 bucks and, this comes on a nifty acrylic wand I made so you can submerse it into the water up to 24" of depth. Heat shrunk, and with electrical wire whip, long enough to connect to a meter (you provide the meter - any AC/DC meter will work).
$SOLD sounds reasonable. .. or OBO
Best to email me; JohnnyAirtime [at] gmail [dot] com
I found this old picture, of me using it in my 24" deep 240gal tank;
The photodiode, on the end of the acrylic;
Overall;