I have been using a Lenovo Thinkpad Helix for months now, successfully replacing 4 towers, 1 laptop, 1 iPad, and 1 Android tablet with the single all-in-one device. It has been great! Now, I am ready to add a GSM SIM card and get this thing fully mobile.
I had no idea what the IMEI is on the device as there is no sticker and I don't have the original box or documentation. After a little searching, I found a handy command that works in Windows command line: '$ netsh mbn show interface'
This produces the following results: