However, it's important to note that not all postcards are primary sources. If the postcard was created after the event or experience it is being used to study, or if it is a reproduction or copy of an original postcard, then it would not be considered a primary source. Additionally, if the postcard is being used to study something other than the event or experience depicted on the postcard itself, it may not be considered a primary source. For example, if the postcard is being used to study the history of postal services or the evolution of postcard design, it may not be considered a primary source for studying the specific event or experience depicted on the postcard.
Therefore, the determination of whether a postcard is a primary source or not depends on the specific research question or purpose for which it is being used. If the postcard was created during the time period being studied and provides firsthand information or observations about the event or experience, it can be considered a primary source.