Seamed, butted, manganese alloy tubeset from the late 1980s. Ecomonical but on the heavy side. Used primarily on lower mid-range models and, because of it's extra weight and durability, grand touring models. A good tubeset for the price and intneded use, but like all tubesets, the ultimate ride characteristics and quality have more to do with the geometry selected by the designer and the skills of the framebuilder.
Not familiar with the PT-4500 but have seen the PT-3500 and PT-5000 which seem like nice bicycles for the prospective price points. The Panasonic brand always had a good reputation based on the owners that I've talked to, though I never sold them and have only ridden a few race models.