Welding Tips and Tricks

Hey guy! Hope everyone has had an awesome day. Yesterday one of my fellow classmates gave me a couple of old gas cylinders. One of them for sure is acetylene and the other one im not sure what is in it as the cylinder is old and in rough shape. Can anyone ID this? Thanks guys

I'm not an expert, but what does the outlet coupling look like?
Since the fitting threads are fairly application-specific, I'd think that would tell you more than the neck markings unless it was a low-pressure cylinder for CO2.