R.G. Dun & Company

later Dun & Bradstreet

Obispo & Cuba (Banco Nacional building), Havana, Cuba

This firm produced perfins from 1911 to 1938.

Here are a few DUN perfined covers:

Used 10 February 19-- from Bayamo to Buffalo, New York, USA
This is most likely an unauthorized usage (Note: the sender filled in the perfs with a pen!)
DUN perfin on a 2¢ Máximo Gómez definitive (1930) - Scott 309, Edifil 252

Used 4 April 1923 to another R.G. Dun office in Jacksonville, FL
DUN perfin on a 3¢ José de la Luz definitive (1917) - Scott 267, Edifil 207

Used 29 May 1934 from Havana to St. Louis, Missouri, USA
DUN perfin on a 2¢ over 3¢ overprint José de la Luz definitive (1933) - Scott 318, Edifil 273

Used 23 June 1936 from Havana to London, England
DUN perfins on two 2¢ Máximo Gómez definitives (1930) - Scott 309, Edifil 252
DUN perfin on 1¢ José Martí definitive (1930) - Scott 308, Edifil 251

A word about "control holes":

The DUN perfin without control holes was previously listed in the World Perfin Catalog - American Section as "A5a". Since that time, several DUN perfins with one control hole have been identified. Based upon the finding of a block of four with a pair with no control holes and a pair with just one control hole, it is now believed that there was but one multiple die machine with numerous pin breaks resulting in the all three combinations.

Pin breaks abound with DUN. Note, however that the one control hole variety comes from one particular die with one or two pins broken in the "D", no pins broken in the "u" and three pins broken in the "n".

Here are some of the stamps which have DUN perfins.