In the internal memory of my GO 720 I cannot find the file "system".
The navcore version is 9.430. The ttgo.bif-file says that the bootloader
has version 55120. Where is that bootloader stored?
The GO 720 is functioning ok.

Don't worry, both your BL and your NC are fine.
Since the 9.430 did not come with a bootloader you might have deleted it earlier, it is only used once and after that stays in the permanent flash memory.

guek4000 wrote:The ttgo.bif-file says that the bootloader has version 55120.

5.5120 is the navcore 8.351 BL. I concur with Downunder, 5.5120 is fine, so leave it alone.