"Crosby Mod" type of grill (steel), pro audio speaker terminals and side handles mainly.
Difference between Quad ESL63 Pro and Quad USA mon
What are the difference between ESL63 Pro and USA monitor and normal ESL 63? Some said difference in steel gill ( pro ) and aluminium (USA monitor and normal ESL 63); Other said both pro and USA monitor use still grill while normal 63 use aluminium grill. Please advise.