unused --, 1924, 1c Deep Green, type A overprint, 'Canal' and 'Zone Canal' varieties (71c, 71d), top margin vertical combination pair, top stamp the 'Canal' only variety, fresh, well-centered, usual slightly tropical o.g., negligible narrow natural gum skip at T., very fine, scarce, 20 and 180 examples of each exist respectively, Scott retail $2,200.00+ photo est.