Dating postcard stamp boxes
Light energy alone, usually from the sun, reacted with the light sensitive chemicals on the paper’s surface to produce an image.They only needed to be fixed to preserve the exposed image.
Some halftone cards were printed on high gloss paper to resemble a photograph but their screen patterns will give them away if one is vigilant.
Today there are many real photo postcards of unknown origin and date.
When no postmark is available, the type of materials used can often aid in narrowing down the years it may have been produced in.
This could go on for generations, and it is not uncommon to find the same photograph attributed to three different artists.
While today this would lead to lawsuits, copyright was uncommon and rarely enforced at the turn of the 20th century.