hp 21mx E on ebay (question/comment)

I looked a while ago at the HP 21MX E series on ebay. Just now happened to come across it again at http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2772816038&categ… The unit says 21MX-E on the front, and also clearly says "E series computer". However, the tag on the back says 2112A, which was an M series machine. Odd. But further still... the keyswitch has positions operate, standby, R, and lock. This was indicative of M series machines I thought. True enough, M series were often upgraded to E series via a motherboard upgrade. But the rotary key switch is obviously still connected. And from what I've seen, M series upgraded to E they generally didn't take the time to upgrade the front panel silkscreen. I'm betting it's an M series. Or maybe an M that was very completely upgraded to an E. Anyone have thoughts on this? Regards, Jay West