•  Frames, like architecture, are identified based on the region and style of construction, such as French Baroque, Italian Renaissance, Rococo or Neoclassical. By the 19th century, it became the fashion to reproduce many of the previous historical styles. These frames are described using terms such as "Rococo revival" or "Louis XV style".

•  The wood on the backs of antique frames should show the marks of hand tools. Plane blade marks, handsaw marks, and irregularities in the surface are all indications of age. A perfectly flat surface on the back of a frame indicates manufacture using modern power tools.  

•  Antique frames, especially of European origin, often show signs of insect infestation, characterized by small round holes in the wood.

•  Wood type can be an indicator of the region where a frame was made, as most frames were made of locally available materials. Italian Renaissance and Baroque frames, for example, are normally walnut or poplar, while French Baroque frames are oak or linden and English frames are usually Scots pine or limewood. Early American frames, which were produced almost exclusively on the east coast, are invariably eastern white pine.

•  The way in which the frame members of a frame are attached to one another, known as the joinery, show distinct regional differences. For example, early French frames are always joined with spliced mitered corners, while most early Italian frames feature lap-jointed corners.

•  Until the end of the 18th century, the decoration on most frames was carved into the wood by hand. Cast materials, generally plaster and a flexible casting material called compo or composition, came into popular use in the 19th century. While the backs of the frames remained wood, the decorative elements were cast separately and attached during construction. Revival style or reproduction frames are usually made using cast materials.

•  Most high quality frames are finished with gold leaf. Genuine gold leaf can be differentiated from imitation gold by the size of the sheets, which can often be seen on close inspection. Genuine gold leaf is 3 3/8" square while imitation gold is 5" square. Bronze powder finishes, in comparison, generally have a dull luster and gritty texture. Some fine frames are finished with silver leaf, and silver leaf was often covered with an orange tinted varnish to imitate gold.  

•  Leaf finishes usually become abraded as they age, and the color of the gilder's clay under the leaf, known as the bole layer, will begin to show through.   Bole is available in several colors, and regional preferences can help to identify a frame's place of origin. A combination of yellow and red clay, for example, is typical of French 18th century frames, while gray or black is common in 19th century European and American frames.

•  A frame's condition and patina, the antique appearance that develops over time, isn't always the best way to determine its origin and age. A frame with no structural damage and bright gilding is either of modern construction or has been recently regilded. Reproduction frames, however, are often subjected to a process of intentional "artificial patination" or "antiquing" to simulate an antique finish. In addition, many antique frames have been partly or entirely refinished over the course of their lives, often multiple times with a wide variety of materials.

It takes years of experience looking at thousands of frames to develop the ability to correctly identify their places and dates of origin, and to be able to assess what has happened to the frame in terms of its condition. When in doubt, contact an appraiser or conservation professional for further guidance.