What is the error on the 2007 Montana quarter?

Can you clarify the specifics of the alleged error on the 2007 Montana quarter? Are you referring to a minting mistake, such as a misaligned die or an unusual marking? Alternatively, are you suggesting an anomaly in the design or composition of the coin? Without further details, it's difficult to pinpoint the exact nature of the error you're inquiring about. Can you elaborate on what makes you believe there's an error on this particular quarter?