$20 Gold Saint-Gaudens High-Relief Masterpiece - 10mm version of the original 1907 Saint-Gaudens design commissioned by President Theodore Roosevelt. Includes certificate of authenticity and official archive registration form with each coin.
It is hard to say without seeing a photo of the coin and a copy of the certificate. 1907 Saint-Gaudens Double Eagles were indeed initially struck with a high-relief dye and are very rare. They measure 34mm in diameter, not 10mm.
If you can post images of the coin and the certificate it would be easier to see exactly what coin you have.