Dating Portraits - Notched/Beveled Edges

Flat edges may also be gilt however, so to determine if a gilt edge is beveled, look at it with a bright light behind you. Start with the card face toward you, and gradually turn it until the edge faces you. If the edge is shiny mid-way through that process, then the edge is beveled, if it only gets shiny when the edge is directly toward you (so the face of the card is at a 90 degree angle), then the edge is straight.

Dating:

Beveled edges were popular 1875-1900. Notched edges were common 1894-1900.

Observations:

Darrah doesn't mention square gilt edges, but they seem to have started a bit before the beveled edge, ca. 1870, and continued in use through to 1900. I haven't done any actual statistical measurements yet, but offhand it seems that the presence of beveled or notched edges is one of the more reliable indicators of a late CDV, and it seems likely that the same dates will be found to apply to Cabinet Cards.