This firm produced perfins from 1884 to 1896.
Here are two Bartning Sucs. covers produced in that time:
Used 14 April 1892 from Mazatlan to New York City
"B" perfin on 5 centavos Numeral in Oval definitive - Scott 216 (1890) and in five 20 centavos Numeral in Oval - Scott 220 (1890).
Used 1 April 1890 from Mazatlan to Jersey City Heights, New York.
"B" perfin on 5 centavos Numeral in Oval definitive - Scott 216 (1890).
Used 27 July 1884 from Mazatlan to Manzanillo
"B" perfin on 5 centavos Hildalgo definitive - Scott 154 (1884).
Here are some of the stamps which have Bartning "B" perfins:
Bartning Sucesores building.