Check out the website for the drug company Actavis. The description of Gabapentin 300mg (a brand equivalent of the drug neurontin) is a "light brown/yellow capsule with R2666 in black ink. My son said a friend of his had these and thinks they're oxycontin.
Light brown/yellow capsule with imprint R2666 w/black ink is equivalent to Neurontin, which states it is for seizures and pain from shingles/herpes. I don't find anything indicating that it is oxycontin.