Where would I find biographical information on assayer Diego de la Torre? Only info I have is he was assayer at Lima, Peru mint 1577-1588, his mark was a 'D' - Star of the Magi added, and Phillip II ruled Spain.
His name is spelled and written the same as mine with the small 'd', small 'l', and the capital 'T'.
He was a silversmith who lived in Lima between XVI and XVIIth centuries. There is a very good article about the silversmiths working in Lima in that period, where you can find information about him and all the officials of that mint: http://institucional.us.es/revistas/arte/02/04%20heredia.pdf
There is an online book about the mints in South America in the colonial period. It has a chapter about the temporary reopening of Lima mint, when Diego de la Torre worked there: http://www.tesorillo.com/articulos/libro/214.htm
These are some online resources where you can find information on Diego de la Torre, all in Spanish.