These are actually kg/cm2 but that is the same as bar. At least close enough for diving. 1 kg/cm2 equals 0.98 bar
These are NOT your standard fitting for a hose. These gauges are new but very old. I would love to know their history but I suspect well over 40 years old. I believe these came from Sunfish. Sunfish was a store in Calgary in the early 2000's. I bet Sunfish bought them from Bob's Scuba Metric, which was also a store in Calgary in the 90's . The hose fitting is the same size as your low pressure port on your first stage. The gauge will NOT work on that port. It must go on a high pressure port. You could try an adapter. I do sell those as well.
The price represents the age but not the story !! Plus they come in a cool retro box !!