These are Waterway Plastics Spring Check Valves in two different spring strengths.
The 600-8140 Waterway Plastics Spring Check Valve is made with a 1/4 Pound spring and is used as an air blower check valve.
The 600-8150 Waterway Plastics Spring Check Valve is made with an 8 Pound spring and is designed to be an automatic water bypass valve.