There are two or three manufactures of basic depth sounders. Hummingbird, Hawkeye, and Uniden. There could be others, but if you can provide a picture we might be able to help you out. The buttons should give away what manufacture it is.
Or you could call Sanger directly (559)485-2842. If they installed it, you should be able to give them your Hull number and they could look up the build sheet.