We lived a couple of miles from the Highland Park tower, and even in the early '70s, many numbers were still using or given exchanges. Ours [[491-) covered most of the Meyers Grove area, a vast majority of those numbers residential north of Lyndon, and industrial closer to Grand River. But we never had an alphanumeric code prefix. Why is that? Had the company phased it out by then, or was this a 'new' number without it?