1957 Meguro S3 on display at the 2014 VJMC-Hinshaw's Motorcycle Show n Shine -- Auburn, Wa.

Meguro was a major motorcycle manufacturer in post-war Japan.  The company was bought by Kawasaki Heavy Industries.  

Yes,  it's a Japanese Amal.  In the 1950s Amals were produced under license in Japan.  Many Japanese motorcycle manufacturers (even Honda) used Amals on their bikes.