It may well be that the NA GTM60 and EU GTM70 run the same firmware but I wouldn't have thought so. My NA 3597LMTHD [supplied with GTM60] and a friend's AU 3597LM [supplied with FM only GTM3x] both have the file 006B154600.gcd since purchase and those 2 files are identical.

But here's the thing, also identical with them is the file uploaded by SavaSnoo which is from his EU unit with GTM70. I've found references to both 'HD Radio' for NA and 'DAB' for EU in those 3 files in clear text.

However, the file direct from Garmin named FirmwareUpdateforGTMxxDigitalRadioTypeS_230.gcd does have the same size as the above 3 x 006B154600.gcd (1,052,844 bytes) but its hashes are different and on a quick hex check it seems that the file in the Garmin download maybe is encrypted.