Doubt regarding back of IWC Chrono GST ref. 3707

Dear Sirs,
I’ve a doubt concerning the back of a IWC GST Chronograph ref. 3707 in Titan. In the back it is not engraved SCHAFFAUSEN INTERNATIONAL WATCH Co. as in many other pictures I can see on the web. The serial number is 2657741. The dial is in Tritium. The doubt is: is this back not original ? Is it possible that this watch is part - for example - of an initial batch with this peculiar back ? Is the back original but consequence of a later replacement during a service in IWC ? Would you be able to give an explanation ?

Thank you in advance and best regards
Andrea

Can you share a pic of the front please.
That way we can assess the whole watch. The crown looks suspect to me, as well as the caseback.

Here below there are some other pictures of the watch

[](s1126.photobucket.com/user/pomponio69/media/IWC%20GST%20quadrante%202_zpsbc6zqmi0.jpg.html)

[](s1126.photobucket.com/user/pomponio69/media/IWC%20GST%20chiusura%202_zpswx2ucpji.jpg.html)

[](s1126.photobucket.com/user/pomponio69/media/IWC%20GST%20lato%20pulsanti_zps6jcqb2ut.jpg.html)

[](s1126.photobucket.com/user/pomponio69/media/IWC%20GST%20lato_zpspudtnlbp.jpg.html)

[](s1126.photobucket.com/user/pomponio69/media/20160904_113557_resized_zps0ugg5vgn.jpg.html)

Thanks for the additional pictures.
The crown is displaying properly and appears to be good here.
It's full set, hard to say what happened to the caseback. Looks like it's been ground down completely for some reason.