My /mnt/secure/device.cfg also ends with
Code:
webStoreToolbar=simpletoolbar
#5df79580
And in addition I have a device.cfg.back and a device.cfg~ with different content. I don't remember if I have ever edited this file with this or that editor creating backups (e.g. emacs -> ~), but it might simply be that some firmware updaters in the past did the job and left their signature.