IO, as the yanks say, whatever...... You may be happy to encourage people to risk blowing themselves up, I am not.
I go through around 100 J Cylinders a month in my diving business with our own dedicated account manager with Air Liquide who probably know a damn site more about gas standards than a man with rented welding O2 cylinder in his garage.......
The working pressure of your 1st stage is 137 bar. The first stage is based on a medical oxygen kit and use common parts, the contents gauge should go up to about 180 bar, that does not mean it is safe to use the 1st stage at that pressure. But what would I know......
It also strikes me that you have been unlucky with the dive centre refills, everyone I have supplied cylinders and adaptors to has not had a problem. But then they are filling CE Marked European cylinders with the correct filling adaptor......