sinuhe: Hi,
what is the difference and how can I tell what version a particular BV7 is? When was the upgrade done?
One big difference is the quality of the panel. The MKII had an updated panel that was significantly brighter and with a higher contrast ratio. The only reason I was aware of this was when my MKI went in for repair - two years after purchase - and I was lent a MKII whilst it was in repair. When it came back, I quickly realised the panel was way darker (you could call it 'gloomy' in appearance).
I think the MKII came with HDCP support as I was able to connect directly to my Sky HD box.
I'd probably recommend a second hand MKII. It's better than my new BV7-40 MKIII showing SD channels, certainly SD-based football. It's good for HD, too, although only has 1 DVI socket.