How to tell which Edition/Version of Windows was OEM?

As in my previous question, I'm working on reverting my ASUS 10TP system back to 8.1 so I can reinstall.

I installed 10TP near the beginning of the release cycles, this month I discovered that I couldn't just continue from 10TP to the full version of 10 (see other question). According to Microsoft, I need to downgrade to 8.1 using the media creation tool on another computer and reupgrade to 10 following one of the "correct paths."

Because I thought that getting 10TP on an OEM Windows PC was equivalent to the prereleases of say, Linux (silly me) and would eventually update, I didn't write down my product key or OS variant prior to running the media creation tool and getting 10TP. It happily installed and has been running well until I got the scary "I'm committing suicide" messages on Oct 1.

I have downloaded the Windows 8.1 Media Creation Tool on another PC per Microsoft's instructions. I used Nirsoft's Produkey to read the Windows (BIOS OEM key), downloaded Windows 8.1 US English 64-bit, burned to DVD, and booted from it.

When I got to the "enter a product key" I got an error:

The product key entered does not match any of the Windows images available for installation. Enter a different product key.

So I downloaded and burned Windows 8.1 Pro (Since I have 10TP Pro), same error.

I still have the box the computer came in. It says:

OS TYPE:WIN8.1 64BIT-WITH BING

KB LANGUAGE:US

Just for fun, I used Produkey to grab the Bios OEM Key from my personal laptop. Plugging in that number into the Windows8.1 disc worked (no error). Of course, I've already got a computer with this key so I don't imagine it will work if I actually installed.

I'm going to try the steps detailed over on Clean install Windows 8.1 or Windows 8 from OEM key, but is there a way to tell what (Windows) OS was on the computer to begin with?

For future reference the Windows 8.1 Editions given in the media creation tool are:

Windows 8.1

Windows 8.1 N

Windows 8.1 Pro

Windows 8.1 Pro N

Windows 8.1 Single Language

Each with a 32 or 64 bit option.

Answer

Windows 8.1 With Bing is a special edition supplied to OEMs. At the very bottom of Create Installation Media for Windows 8.1, the fine print includes:

If you're running Windows 8.1 with Bing, contact your device manufacturer for info on how to get installation media for your edition of Windows.

In other words, Windows 8.1 with Bing cannot be reinstalled from a microsoft-provided ISO.

I do not know how to figure which version of Windows was OEM installed from within the OS.