This firm produced perfins from 1917 to 1925.

Well, darn it! I would like to illustrate a cover where a FRCo perfin stamp is on an envelope with a printed Frank Robins Co. corner card. Instead, I have only found FRCo perfin stamps on three picture postcards, all from the same fellow, to his sons and mother back home in Augusta, Illinois, written over the span of 1½ years. An obituary on the internet for the writer, Ralph W. Crain, states that he lived in Havana from 1908 to 1932, working as a representative for the Remington Typewriter Company in Havana. A 1921 Printer's Ink publication states the following:
That is the first connection of the postcard writer to the Frank Robins Co. – Ralph Crain's good friend, Mr. Rose, worked for that company.
I then emailed someone that I found on a genealogical site and received not only a picture of Ralph W. Crain, his wife and two sons (shown at right, ca. 1910), but also a passport renewal application, signed by Ralph W. Crain, from 1918. In part it reads,
I now know for certain that the writer of the three postcards using FRCo perfins worked for the Frank Robins Co. This is the proof needed to establish ownership of the perfins just short of having a cover with a Frank Robins corner card and perfin stamp. Ralph W. Crain was using the stamps of his company to write home to his mother and two sons who were staying with his mother while attending high school in the U.S.
Used 11 September 1922 to Augusta, Illinois, USA, by Ralph W. Crain, an employee of the Frank Robins Co.
Perfin on 1¢ José Martí definitive (1917) - Scott 264, Edifil 205
Used 12 November 1923 to Augusta, Illinois, USA, by an employee of the Frank Robins Co.
Perfin on 2¢ Máximo Gómez definitive (1918) - Scott 266, Edifil 206a
Used 5 May 1924 to Augusta, Illinois, USA, by an employee of the Frank Robins Co.
Perfin on 1¢ José Martí definitive (1917) - Scott 264, Edifil 205
And here are some FRCo perfins: