All right, first off NH3 is never stored in bottles, I have never personally seen NH3 stored in stainless, however that does not mean shit. The picture most definitely shows a propane tank (not stainless), however I would bet my next paycheck that it contained NH3. Yes if one wanted to store NH3 in a propane tank long term, one would have to replace the valves with stainless hardware, however a propane tank is built very well, worst case scenario, a small amount of pitting would be evident on the inside of the propane tank after a few months of storing NH3, (if the proper hardware was in place). And yes a nurse tank is a very large mobile tank, I think I have posted some dimensions and identification of nurse tanks here, and no they are not stainless steel......
And by the way...........
Wrong Forum, UTFSE........
much_love
methyl_ethyl