Puerto Rico. Mostly used. 100s of stamps from the 1870s onwards mint and used, these of course being under the Spanish Administration, all housed in one volume. Then American Administration inc a study of 36 degrees/25 degree o/ps with values from 1cts to 10cts, lots of pmks to research, approximately 100 stamps here for this category as well, finally ending with further 'work in progress' 19th century back of the book.