Hi James. I don't see that you uploaded an image, but I assume you are referring to the "Jumbo Coffee" stamps of 1984. They are listed as ISGC # 1538 and 1539, with 5,000 copies of each printed. One million each of the regular sized coffee stamps were printed, except for C789 (25c), which had half that amount printed. The 2013 Scott catalog mentions the Jumbo Coffee stamps in a note at $80 and $110 respectively, but they are not assigned Scott #'s. I found a set of the two Jumbos listed on ebay just now for $125.
From an article in El Quetzal #246, April 1985:
THE JUMBO STAMPS: The decree originally called for two souvenir sheets (hojas miniaturas). As a result of some confusion, the sheets of six were perforated and thus lost their status as souvenir sheets.
I remember hearing about some controversy surrounding the sale and resale of the Jumbos in Guatemala. I was able to find this in EQ #316, November 2003, about dealer Kurt Weiss:
Kurt was involved in some way and profited from the Coffee jumbos. We don't know how many he acquired for resale, but did well. He would proudly show off the large television in his living room, and a new refrigerator, commenting that both had been funded from the sale of the Jumbos.
Eric Dyck
Librarian and Website Administrator
ISGC