REED VALVE ASSEMBLY (similar to 431-13610-01)
Don't know what the story is with this one, but have never seen one before.

Comparison:

Flange hole centres: 52 x 71mm (same as 431)
Flange: 83 x 64mm (same as 431)
Exterior Reed Housing: 62mm wide (431 is 59.5mm)
Interior Reed Outlet: 57 x 36.5mm (431 is 55 x 31mm)
Reed housing height: 45.5mm (431 is 43.5)
Standard 431 Reeds will fit

Beautifully made :-)

1 Only