A year and a half ago, I wrote up a post lamenting the problems caused by counterfeit USB to serial adapter chips.
One of the primary issues was the inability to tell the adapters apart on the USB device tree when hooked up to the same computer. (There were, of course, other problems.)
Amazingly, after revisiting the thought recently, I discovered that any of the cheap adapters built atop the Silicon Labs CP210x chipset would in fact allow you to set the serial number to a value of your choosing!
In fact, they have manufacturing tools (CP210x Legacy Programming Utilities) that make this unavoidably easy:
Once the new device serial number is programmed in, it should be possible to address the device by name using specific udev rules.
On Windows, you can set the device to a specific COM port number, and Windows will assign it to that number when reattaching the device. So statically assigned / named USB serial port adapters are possible.
This opens up whole new possibilities in testing hardware or interfacing devices still using serial communications (old-school, non-wireless IoT nodes, for example).
Just make sure that when you’re getting the adapters off of eBay, that they’re using the right chip!