It said that the famous photographer Disderi invented the carte-de-visite (CDV) in France in 1854, but the basic concept is so obvious, surely someone else thought to mount paper prints on stiff cardboard backing.It is the standardization of size, however, that makes Disderi's contribution so notable.By 1862 they become commonplace, and by 1865 they completely eclipse all cased images.
Personally, I think a TRUE CDV should also meet my Card Mount Criteria.
The first step in dating 19th century photographs is identifying which technology was used to create the picture.
This is straightforward detective work for most images, but very early photographs can be misleading.
Hence I developed my Card Mount Criteria to distinguish between true card mounts, and simple matted images. ): To be a true card mount, the print should be 90% or more of the total card width or height.
This criteria does not apply to stereo-cards, though they often meet it anyhow.