the solenoid serves no purpose. HOnestly that looks like it was used for a saltwater/reef aquarium's calcium reactor, or a freshwater planted tank. You run the solenoid valve on a pH meter or timer so it doesn't 'overdo' the CO2 in the water.
I can't see close enough but your low pressure gauge will need to be accurate between 5psi and 30psi. you can change out the gauge if its not the right range, but for the cost of doing that I'd rather buy a new regulator.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10