It's a very nice PDG Series Paramount made by National/Panasonic in Japan for Schwinn using Tange/PDG OS tubing. Your best source of information about it would be Marc Muller at Waterford Precision Cycles. It's fairly rare in that it wasn't a "numbered" Series bike (Series 2, Series 3, Series 5, Series 7) and didn't, to my knowledge, appear in the Paramount catalogs.