The arrows are painted on the face of the gauge. That particular photo is from the COBIA but I saw similar markings on the shallow depth gauges of PAMPANITO a couple weeks back. I also dug up some photos online from COD and it also has the markings although they are at very different depths.
I'm very stumped. Your expert opinion is very welcome.
Also, I can't wait for your SARGO guide!
Thanks, Dave!