@knc1: IIRC, that may be what's printed on the back of the device as "model name".
@djsmiley2k: In any case, as @knc1 just demonstrated, this is not how we're expecting you to ID your device (see
https://wiki.mobileread.com/wiki/Kindle_Serial_Numbers)

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Regarding your issue, this is a known issue with old packages (i.e., those packaged by the legacy python packager, not KindleTool), and those "new" firmware updates.
I thought someone (@eschwartz, maybe?) had taken care of updating the posts, but I may have dreamed that one up

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In any case, it's trivial to repackage something, see the last few pages of the
KindleTool thread for details.
EDIT: ... or maybe the *first* few pages, actually. Lemme dig that up...
EDITē: Those kind of posts were actually scattered all around the place, and not necessarily in the KT thread, so, let's continue that tradition:
Code:
kindletool convert Update_foo.bin
kindletool create ota -d k3gb Update_foo_converted.tar.gz Update_foo.bin
Making sure the target device actually matches your own device. That's an European 3G Kindle 3 in my example.