These are PN32 3/81/2" BSP Globe Valves to suit Traction Engines/Steam Boats/Marine Engines etc.
As can be seen in the photographs there are 2 options for the valves.

These are rated for 450 PSI Safe working pressure and are what is fitted to our 6" Scale Fodens working at 200 PSI.

Options available are: 

1x 3/8" BSP Globe Valve

1x 1/2" BSP Globe Valve + 2x 3/8" BSP Barrell Nipple