I have worked in the past for an LDS and I can tell you that we get in all kinds of tanks in all kinds of conditions. All I would check for is the VIP sticker. If it was an O2 sticker and they had the correct type o-ring, then I would do a Nitrox fill. It did not have to have any other kind of markings on it.
We did partial fills for Nitrox so it was very important that the tank AND valve be O2 clean. Our procedure was to fill a tank, that I had previously emptied, with 100% medical grade O2 to a designated pressure (this would depend on cylinder size, the ending pressure and the desired percentage of customer). Once that pressure was achived, I would let the tank cool off and then top it off back to the desired pressure. I would then fill the tank on the regular system up to the working pressure. I would then let the tank cool off again (which always dropped the pressure back a couple of hundred PSI) and top off again. I would then come back after a couple of hours and test the mix. I would consistantly get within a couple of 10ths of a percent of the required percentage. Say the customer wanted 36%, my final readings would not be off by more than half a percent and most times was right on the money. That is why we charged more for Nitrox fills, becuase of the hassle of filling them up. Now if the shop owner would fork over the money to have a pre-mixed station, that would be a different matter. However, most of the divers that came into our shop were also diving other mixes besides 32 and 36 (Can we say stage bottles). If I saw a stage bottle with MOD markings on it I didn't check for anything else except for the hydro stamp. As long as it was not out by more than a year, I filled the tank with the condition that the next time the customer came in with that tank, it would have to be hydro'd before I would fill it.
Since I was the one doing the filling (and it was my life and limb on the line) you had to play by my rules. I personally don't think that is asking too much. If you want to fill your own tanks and use your own compressor to do it, then by all means do so. If another shop does not want to fill your tank because it does not have a green and yellow band around it, then take it elsewhere to get it filled. If that is not an option, then try (very diplomatically) to explain to the personnel of the LDS that a tank has to be clearly marked and the VIP sticker should satisfy that requirement. If they say it doesn't, then ask them to show you a printed rule book where it states that is the case. They will of course be unable to provide you with such as there isn't one.
