The buckle is made of light weight (33grams) hypoallergenic Titanium with a sand blast Finish. Its designed for a 1-1/2" leather strap. 
If you're looking for more than just cheap plated metal this is grade 2 Titanium . (Buckle only)
Only available form Burch Belts.

There has been a 40 percent increase in the number of people tested positive for nickel allergies over the last five years, according to the American Academy of Dermatology, And the numbers are growing. The American Academy of Dermatology recommends products made of alternative metals like Titanium.