Coro G.I. Marked USMC EGA MP Brass Buckle Hardware Dating?

[Travd3]

The buckle in the photos came as a set of Vietnam era white USMC MP gear.  This is the first time I have seen CORO marked on a buckle.  It is also marked on the brass keeper. Any idea as to when and for how long they made these? I understand CORO when out of business sometime around 1979.

[Travd3]

I took the EGA off and it is not marked.  

[Brig]

Between 1960 and the company's shuttering in 1979

[Travd3]

Thank you