I've had one genuine Garmin mount and two cheap copies. I know have only two and I honestly don't know which they are.
My two genuine silly-expensive mounts have embossed print on the back which says TAIWAN
My two cheap knock-off (in every sense) ones don't.
The genuine ones are such a tight fit that I snapped one of them in two while trying to detach the Etrex. Although what is left is now only half the length, it is still a good tight fit and quite secure enough and is now my preferred mount. I always use a lanyard but it has never actually deployed. It's criminal that Garmin don't include a lanyard in the bubble pack for these Etrexes, which are after all aimed primarily at walkers.
Although these are invariably marketed as 'Oregon' mounts, Garmin refer to this as their 'spine mount' system - with variants for handlebars, dashboard vents etc.