Scott lists 25 varieties. SG and Michel each list 27. SOFICHE Chilean speciality catalogue) lists 234 varieties!
The "Seymour Family" website includes a display of the Hamilton Collection. Great visual reference.
The Sociedad Filatelica de Chile site includes link to downloadable versions of the entire run of "Chile Specialist". English-language newsletter which ceased publication in 2009. Have yet to find/locate an index.
Another valuable resource is classic latin america (no spacing) dot com.