"As King says, original factory finish is metallic black."
My 79 GTS 9138 is Metallic Black Finish in places where it could have been a mat black finish. The Original Invoice states Bianco / Nero no mention of metallic. 78 & 79 Lincoln Mercury did produce a metallic black and seems fit for the era.
My 2 cents
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.