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HankronAdam, I had forgotten to mention that your photograph isn't technically a Panel Card, as Panel Cards are larger. I don't know the name for your sized-photo, though there may be one. Just realize that, other qualities even, the larger the 19th century photo the more desirable and rarer. So that yours is larger than normal is good.
One last point, a generic term to cover all these types of photographs (paper photograph pasted to a cardboard backing) is either 'mounted photograph' or 'card photograph.' You will notice that they are all called 'cabinet CARD', 'Panel CARD', 'tobacco CARD.' Even Cartes de Visite (CDV) is French for 'visiting card.'
In other words, it's perfectly acceptable to call an odd size, a "card photograph bigger than a cabinet card."