Bicycle component maker in 1930s ~ 60s.
There may be a connection with Officine Mecchaniche Giostra who produced Magistroni components and later became Ofmega.
 
Updated 10.10.2017 
Click pictures for a larger view

State-of-the-art crank set

Walter Lai pic
from BicycleSpecialities site

   Ads from the 1950s

Double sided hub. 

A pair of hubs, circa 1940s
 on eBay by seller 8leicester