A simple way to inspect the craftsmanship is to study the solder lines. The solder lines on a good Tiffany style lamp is finely drawn, even, and well polished. They are firm and usually plump, supporting the glass artwork and holding the shades tight. The solder on a low quality Tiffany style lamp is inconsistent - thick at some places and thin at other places. You can easily see break-down joints and flat shapes throughout the solder framework.
Touch the shade and see for yourself. The lampshade of a fine Tiffany style lamp feels like one coherent surface, with smooth and even solder lines separating glass pieces. When you touch the surface of a cheap duplicate, your hands won’t have much satisfaction. The solder lines are rough, and if you are not careful, some of them may cut your fingers.
