The manufacturer is indeed SM. GERZAT,
I found this article on a french forum that explained what iain/hsm said.
SM. GERZAT N°24317 . ---> I think this is the model, so its' not a 5000 range.. Does anyone have any information on it
Dude when a random guy on the internet identifies correctly the manufacturer of your cylinders from a crappy photo of a tin box and a couple of blue cylinders I would take note. And when in addition you were told the correct material used in the manufacture (the 5000 series) namley 5283 alloy I would heed the information.
Now finally. The 24317 is the serial number of the cylinder not the material and as this is now twice you have called my information there will not be a third time. You are on your own, your call. Good luck.