You either have a Fan Photo or the More Desirable Movie Still:
Fan Photo:
These were issued in sizes as small as 3-1/2” X 5” up to 8” X 10” and even 9" X 12", but the most common and most popular are the 5” x 7”. These are the photos a fan would receive in response when writing to their favorite star in care of the studio. They were mass-produced, but high quality photos printed on heavy double-weight stock. They usually carry a facsimile signature, sometimes printed into the negative, other times stamped. Sometimes you'll see a mark identifying the original photographer or studio responsible for the photo, again this information is sometimes seen in the photo negative or sometimes stamped right on back.
Although a much rarer find, sometimes you can acquire these photos with their original mailers, which contain a studio return address, sometimes an ad promoting the star’s latest film, and are postmarked giving an exact date of origin as well.
The 5x7’s seem to be the standard from the late-1910’s through the early-1940’s and then there seems to be a switch over to the smaller sizes (perhaps due to World War II?).
The larger photos were available at a premium to collectors—often the 5x7’s would have a redemption stamp on back offering an 8x10 in exchange for 25 cents.
or
Movie Still aka Publicity Photo
These are all members of the same family, real photographs issued directly by the studio to promote the latest stars and their movies. They were included in press kits, sent to movie theaters to help them promote the latest offerings, and sent to newspapers and magazines for the same reason.
Like movie posters and lobby cards this is an area of great specialization with a huge number of collectors and dealers alike. With a huge market specializing in both standard re-issues and later printings, as well as sometimes shadier later printings of lesser quality, it can sometimes be very difficult to identify original, collectible material.
What follows is a quick primer, but David Cycleback has an incredible online guide loaded with many additional details which is available here.
The safest bet is to purchase Keybook photos, but they are the rarest of the bunch and often carry a heavy premium in price.
Full article here:
https://immortalephemera.com/about-movie-collectibles/