This firm produced perfins from 1917 to 1945.
Here are two EA covers produced in that time:
Used 21 March 1934 to Buffalo, New York, USA
EA perfin on 3¢ José de la Luz definitive (1930) - Scott 310, Edifil 253
Translation of envelope: "Furs, shoemaking and saddlery"
Used 31 July 1934 to New York, NY
EA perfin on 10¢ Estrada Palma definitive (1930) - Scott 307, Edifil 247
Here are some of the stamps which have EA perfins:
Old newspaper photo of the Armaignac business (notice the boot on the sign in the photo).
This photo was sent to me by Pietro Enrico Armaignac, grandson of Enrique Armaignac.