This firm produced perfins from 1914 to 1922.
Here are some BNC covers produced in that time:
Used 18 March 1915 to New York City
BNC perfin on 2˘ Mapita definitive (1915) - Scott 255, Edifil 196A
Used 13 August 1918 to Spezia, Italy
BNC perfin on 5˘ Calixto García definitive (1917) - Scott 268, Edifil 208
Used 3 December 1918 to Chaux de Fonds, Switzerland
BNC perfin on 5˘ Calixto García definitive (1917) - Scott 268, Edifil 208
Used 13 August 1919 to Des Moines, Iowa, USA
BNC perfin on 3˘ José de la Luz Caballero definitive (1917) - Scott 267, Edifil 207
Used 21 March 1922 to Mainz, Germany
BNC perfin on 3˘ José de la Luz Caballero definitive (1917) - Scott 267, Edifil 207
BNC perfin on 2˘ Calixto García definitive (1918) - Scott 266, Edifil 206a
Personal Use — Used 27 October 1920 to Colorado Springs, Colorado, USA
BNC perfin on 2˘ Máximo Gómez definitive (1918) - Scott 266, Edifil 206a
And here are some of the stamps which have BNC perfins: