I can not see any gupdate.gcd file in the .system directory in the E: drive on Garmin nuvi 1690. From what I can see the whole E: drive is 247 914 496 byte in size and contains the following directories:

Directories: Size:
.system 54*710*151 byte
Garmin 50*320 byte
GPX 711*104 byte
Help 3*186*189 byte
Keyboard 931*676 byte
Text 47*529*055 byte
Veichle 1*220*608 byte
Voice 131*464*448 byte

And these are the folders and files in the .system directory:

Directories: Size:
Diag 2*097*154 byte
FCD 238 byte
RemoteSW 54*710*151 byte
sqlite 2*231*296 byte

Files: Size:
gmapbmap.img 48*766*976 byte
gmaptz.img 590*848 byte
gsm_nvm.txt 1 byte
Locales.xml 98*498 byte

I did copy all directories and files of the device before I formatted it so I have the files from that but there were no .system directory then. I do not know what all files are for so I can not tell if I am missing some, I had to download the Swedish keyboard as it was only US keyboard after the GarminExpress restore but it seems to work fine now.