Do European/Italian light fixtures & boxes use metric threads?
On http://internationalconfig.com/icc6.asp?item=72350-F I found this diagram with M3.5 lugs spaced at 60mm, which matches the mounting plate/mounting strap packaged with the fixture with its inner 60mm rings.
An M3.5 thread is a 3.5mm OD by 0.7mm pitch thread, while an #8-32 thread is 0.164&quot; (4.156mm) with a 1/32&quot; (0.794mm) pitch.  A #6-32 thread is 0.136&quot; (3.45mm) with 1/32&quot; (0.793mm) pitch.  They don't quite match, but visually they look close.