Potbelly, which operates over 280 "antique" sandwich shops in the US, filed on Thursday with the SEC to raise up to $75 million in an initial public offering. The Chicago, Il-based company, which was founded in 1977 and booked $290 million in sales for the 12 months ended June 30, 2013, plans to list on the NASDAQ under the symbol PBPB. Potbelly initially filed confidentially on November 13, 2012. BofA Merrill Lynch and Goldman Sachs are the joint bookrunners on the deal. No pricing terms were disclosed.