They are the Airco Dual Stage gauges. Most folks DON'T like them, because they don't read low pressures (for smaller, home-use torches). Doesn't really matter to me, because I set my torches by 'look,' not by pressure on the gauge. And, the dual-stage will hold the same pressure all day long...no matter how full/empty your bottle is...whereas the single-stage regulators seem to creep in pressure. That only matters when you are welding hours at a time...but it is nice to have dual-stage regulators, when you are using little torches, like the Meco Midget I use all the time.
I don't think they are fluid filled...that looks like a cracked glass. Which means the gauge glass is REALLY glass (and likely older). If you send those in for repair now, they will replace them with plastic gauge glasses.
Anyway, Airco is one of those old, industrial brands, which doesn't get much air time in this brand-focused world. I accidentally bought a set of these with my first set of oxy-acetylene bottles and lucked into them for cheap. After a little research, I'd take these over any single-stage Victor.
One of my favorite things about these is the configuration of the faces of the gauges. It looks a little weird, if you are used to modern gauges, but they are placed so that when you are looking at the gauge, you are standing in the safest place to be opening a regulator...out of the 'blast zone,' when things go bad. Of course, I don't need the guages, for anything but checking to see if the regulator is 'on,' or there is pressure left in the tank. I use sight to determine how much gas to use. But, it is nice to know they were thinking about safety, when they built this set.
It also has a built-in indicator, to tell you when the regulator needs a rebuilt. If the red is showing, time for a rebuild...which also means these were BUILT to be reused, not just thrown away. I like that.
Kev.