Late 80's or early 90's. The newest version of your mixer is 275 watts and has a 4.5 qt. bowl, older versions had a 3.5 or 4 qt. bowl, usually without a handle. Lots of variations over the years with this "entry" model, some had handles on the bowls, some didn't.
My mother had this model for a few years before giving to my sister. I gave mom my 325 watt tilt-head model when I got my crank-up bowl 5 qt. model.