Thanks everyone for this thread! I got a Cisco RNG 150 STB from Comcast. It came with a grey top remote that was pre-programmed for the box and works fine. I wanted a second remote and found one on ebay, cheap, that I thought was the same. When I got it, everything looked the same except it was silver instead of grey. It didn't work and the Cable button programming was locked.

Thanks to this thread, I was able to unlock and enter the proper code. Everything worked except the exit button. Again, this thread gave me the proper EFC code and procedure. What I had thought was going to be a six dollar paperweight is now a fully functioning remote. I couldn't have done it without this thread.