Siemens AG plans a common stock buyback of up to €6 billion ($6.5 billion), or not more than 80 million shares, the German industrial machinery giant said on Monday. The acquired shares will be retired or will be used for employee share programmes, including the issuance to board members of any of Siemens’ affiliated companies and to members of the managing board of the company. The share repurchase programme is lead-managed by a bank mandated by Siemens. The bank will make its trading decisions regarding the timing of purchase of individual shares independent of the company, it said. Currentl…