Why should you know your unit's HWID [Hardware Identification]? Firstly, it enables you to be certain that you are about to flash the correct Unit Software [firmware] to your device. This is particularly important when flashing an RGN file via Updater.exe where an incorrect file may 'brick' the device. So it's essential when undertaking any firmware manipulation such as patching or cross-flashing that the correct HWID firmware be used. Also for any 'modding' that the correct boot.bin be used if it's intended that the existing HWID be unchanged, for example US/EU unit flashed with Asian firmware. It is potentially devastating to use an inappropriate ldr.bin [boot.bin] when flashing via an SD card. The wrong ldr.bin will overwrite regions 5 [the bootloader] and 43 [the 'starting blocks'/X-Loader]. These regions are protected from being 'flashed' [in the way we can freely flash a logo.bin to rgn16 for instance, or restore rgn41/154] therefore the device might be hard-bricked and if it's then not possible to easily write back to them correctly using the proper ldr.bin/boot.bin or rgn there may be no software based situation. It takes but seconds to cross-check your unit's HWID with that of the firmware/bin file you intend using. Use [Only registered and activated users can see links. ], or for newer devices which may not disclose the HWID in RGN Tool (when it just shows "0" instead of the 4 numerals), use [Only registered and activated users can see links. ] to see HWID in hexadecimal then covert it to decimal. Because you can easily check what HWID is written in the firmware file, do it first and maybe save a lot of grief. If the fw intended to be flashed and the recipient device don't have matching HWIDs then don't even attempt a cross-flash unless they are at least the same [Only registered and activated users can see links. ].

Generally, there are two easy methods to find the HWID in a device which isn't 'bricked', and a third method only accessible in preboot mode:

1.
Connect in Mass Storage Mode and look in the folder named 'Garmin' for the file 'GarminDevice.xml'. Open it in a text reader [Notepad, Wordpad etc] or any web browser. Search for first instance of '006-B' or just look near the start for this entry:

<PartNumber>006-Bxxxx-00</PartNumber>

The 4 numerals following '006-B' represented above by 'xxxx' show your unit's HWID.

If you have a backup [and you should have one] then just look at that for the XML file.

2.
Press and hold the Battery Symbol on the main page ['Where To?/View Map'] for ~6 seconds to reach a hidden menu [for some units when on charge, the battery symbol doesn't show so just press where it normally displays].

When the 'SW Ver' page shows, press 'Next'/lower RH corner until you reach a page headed 'Version Information' [some units need only one press, newer units need many presses to get there]. When on 'Version Information' page, press 'Start Test' > 'More'. That will reach the 'Inventory' page and its top 3 lines will show the second horizontal entry as 'Bxxx-00' where 'xxxx' is the HWID. [BTW, the third entry also displays the currently loaded firmware version].

Note that some earlier devices such as nuvi 3xx/6xx series need for the time readout next to the battery symbol to be pressed to enter the hidden menu. They also don't show a 'Start Test' button, so just press 'More' to reach 'Inventory' page.

3.
You can also find the HWID of any unit [even a unit which is 'bricked'] by using [Only registered and activated users can see links. ] but modern units with visible file system must be first put into [Only registered and activated users can see links. ]. Note that devices displaying "System Software Missing" will have defaulted to preboot mode if soft-bricked.

NOTES: Legacy units such as old GPSMAP devices, StreetPilot 27x0/c3x0 etc. which only have flashable regions and don't have a visible file system also don't have a GarminDevice.xml file. Specific info on how to reach the hidden menu on many units is here: [Only registered and activated users can see links. ]. Generally for SP 27x0, BMW Navigator III and similar units, pressing the device's 'Menu' button will show the Inventory page once you're reached the hidden menu [you may have to wait a few seconds]. Some early units may not even have an Inventory page, SP 26x0 for instance. Those 'region only' type devices are in a perpetual 'pseudo preboot' or 'Garmin Mode' anyway so the HWID of all of them can very easily be found by connecting to G7ToWin, just like with any other Garmin unit in preboot mode [even if bricked].