Liquid filled air pressure gauge. This gauge has a glycerine filling that helps dampen the effects of pulsation and vibration, while also perpetually lubricating the movement, and keeping contaminates such as dirt away from all moving parts, which will extend the life of the gauge. 

This gauge reads at 0, 100, 200, 300, 400, and 500 psi. 
Bar reading at 0-35.
 
Specifications:

• Dial size: 2.5"
• Lower mount / Side mount
• Connection size: 1/4" male NPT which measures about 1/2" in diameter.
• Stainless steel case and bezel
• Brass internals & connection (w/ built in snubber)
• Phosphor bronze bourdon tube
• Glycerine filled
• Accuracy: 3-2-3% per ANSI grade B
• Dual scale: PSI and bar (x100=kPa)
• Ambient temperature: 30 F to 160 F