I also have a 2015. It was given to me after being uninstalled from a home. I didn't get any of the original slaves, but have gotten by with some 1950's era intercom slaves that I salvaged from a local high school. They are in mahoganey(sp?) cases with the Nutone brand at the bottom in chrome. They are three wire with call, talk, and listen functions and work well with the 2015. Unfortunately the original speakers inside were no good and were replaced with new speakers of the same size. My fear is that the model number was on the original speakers. If you're interested, drop me a line at my e-mail. email@example.com.