DIR- Generic Marked stages filled with lower O2?

[RainPilot]

There is no single gas that everyone agrees on that goes into a 100, 120, 150, or even a 200 bottle.

Past 20 and 70, the MOD =/= and particular gas although it's usually just no more than 2 options. 120 is 35/25 for some folks and 30/30 for others for instance. 150 is 21/35 for some and 25/25 for others. 190 is usually just 21/35... The disparities are real.

I feel like these "different MOD for same gas" issues could be easily fixed by us all standardizing on a meaning. My take is that MOD is Max Operating Depth with a 1.6 PO2, with TOD being Target Operating Depth with a PO2 of 1.2 or whatever the plan requires.

I mark MOD, even on bottom stages, since if I have a 120' marked tank, even if I plan to switch shallower, that will not lead to a safety concern, whereas in an emergency someone looking at my tank will know that it is switchable up to the marking depth, which gives them and me more options when needing to use that gas for an ascent vs planned bottom stage.

The neck tape with analysis is for me to use, the side / bottom markings are for everyone else to verify or for emergency (eg I hand over a bailout to a diver with lost gas, they can immediately compare the depth to the MOD sticker and make a judgement on what they want to do with it. That of course means that the MOD must be correct for the gas in that tank.