Actually, I believe a buckskin is black+agouti+ 1 cream. 2 creams would be a perlino. A bay is black+agouti.
I am going to go with smoky black as well, he looks sooooo much like the smoky black stud at the farm I board at! He also has black black legs. Since mom was buckskin she could very possibly have passed on the cream gene, and we know dad only passed black.