Most old leaded lamps have some "give". They're usually a little loose or rattle a little. If you find one that is as solid as a brick, it's probably new. Some old shades are solid, so use this rule as a guide, not an absolute.
Handel usually used a fleur de lis pierced cap to support their painted shades. Other genuine caps have a crescent moon or rectangular piercing. They used a different conical reticulated open cap to support their leaded shades. The diameter of the opening for most leaded shades is slightly smaller than for the painted shades. In order for an old leaded shade to fit on a painted cap, the hole had to be reamed out slightly. In other words, if you find a leaded shade on a Handel base that has a cap for painted shades, the shade has been married to the base. It’s also possible that the shade is new and the base is old. That’s even worse.
Handel fleurdelis caps for painted shades have a depth of about " from the top to the supporting rim. Crescent moon caps have a depth of a little less than 1⁄2”. Handel patented this system so that the ring that was attached to the painted shade would slip down onto the cap and be supported by the tiny rim. Somebody, somewhere along the line, got the brilliant idea to make a reproduction cap that had the fleurdelis decoration, but a much smaller depth. This made it very simple to put a new leaded shade on a real Handel base. If you find one of these caps, be careful. Since the cap is new, the leaded shade is almost surely new too.
Handel socket clusters for 18" diameter lamps had three sockets. If the cluster only has two sockets, the base was meant for a 14"16" diameter shade.
Handel lamp bases with reticulated (open work or Oriental style) bottoms are usually unsigned.
Handel almost never used bronze for its lamp bases. They used white metal (spelter). Pairpoint used brass for many of its bases. White metal was used for the intricate bases that were cast in molds. Tiffany and Duffner & Kimberly almost always used bronze for their bases.
Tiffany used a chemical process to produce a patina finish on its lamp bases. The earliest bases had the patina applied directly to the bronze. This resulted in a somewhat poor patina. Experimentation led them to first plate the bases with copper. The chemicals reacted better with the copper plating and produced the best patinas which varied from rich brown to green to red.
White metal does not accept a patina without first plating with copper. Handel and other companies that used white metal plated their bases with copper before applying a patina.
Tiffany used several finishes on their metalware, including lamp bases. Patina finish and gold doré are the most common. The gold finish was applied by electroplating the object with 24K gold. Gold finishes come in smooth or “doré”. “Doré” refers to the acid speckling found on many Tiffany objects. Tiffany also produced an inbetween finish referred to as “statuary bronze doré”. This finish has the acid speckling of gold doré, but is darker. The rarest finish on Tiffany objects is silver. Most probably it was special order.
If the finish has been nearly rubbed off an object, look underneath, under a lid, or somewhere a rag would be difficult to reach. Many times the finish has not been touched in these areas. This way you can get a good idea of what the original finish looked like.
Handel used several finishes. Patina is the most common. Copper plating is also frequently found. The third finish is referred to as “Polychrome”. This finish was hand painted. It is the most fragile of the three finishes. It chips very easily, but can be restored by a good restorer. The copper finish was also fragile. It is rarely found in excellent condition. It wore off easily. The patina finish was the most durable. Many times it can be found in excellent condition.
Patina finishes should never be cleaned with waterbased cleaners or with any abrasive compounds. Any type of wax, from shoe polish to liquid wax to spray wax can be used to revive a dull patina. Apply it and shine it like you would an old pair of shoes. Soft cotton rags work best. Solid waxes will give the shiniest finish. You determine how shiny you want to make the finish. (My personal choice is Minwax liquid wax. It gives a semigloss finish, however I think Minwax may have discontinued their liquid wax.)
The process to apply a patina to bronze has been rediscovered. Some of the new patinas are very good and in many cases are difficult to tell apart from the original. If a base has been totally stripped of its original patina, you might consider having it repatinated. (Cost is a factor here, as the process is not inexpensive.)
Most lamps can be identified by characteristic markers, such as the riser, socket cluster, cap, finial, etc. As an example, Jefferson lamp bases are rarely signed. However, the riser has an elongated star that repeats around the shaft. The socket cluster usually has two sockets, not three as does Handel. The socket cluster cannot be unscrewed as the riser and cluster have been cast as one piece. (Handel socket clusters can be unscrewed.) The cap is not pierced and the finial has a very characteristic shape. Jefferson did not use acorn pull chains.
White metal is an alloy with a high percentage of lead and tin. It is brittle and can snap in half. Bronze is an alloy of mostly copper and some tin. It is malleable and can be bent somewhat without breaking.