Is this a fake GMT Master 1675 Case?

[JagFan]

I just got this 1675 GMT Master, and I am concerned about the authenticity. From the serial number, it appears to be from 1979. I was told the dial was refinished and the hands may be replacements.

I will take it to an authorized dealer tomorrow for authentication, but, in the meantime, I would like to ask your opinions—perhaps to give me a little peace of mind or to make me worry more until then. Among the photos is one of the case back. I cannot find the photo of the movement, but if the case is fake, then the movement will be too.

I would appreciate any info you could offer.