This firm produced perfins from 1917 to 1925.
I am happy to report that a perfin cover has been found and reported by its owner. Responding to our earlier statement that no covers were known to exist, Doug Peterson contacted Rudy Roy and stated that he found one on eBay a few years back. We were delighted to hear the news and receive this proof.
Used from Cienfuegos to New York 2 November 1922
Perfins on 1¢ Martí (1917) and 2¢ Gómez (1918) definitives.
And here are some of the stamps which have O&C perfins: