British Rail Xp64 coaches

Good evening people, something has been bothering me lately. I've been wondering what was the difference between the regular Mk1 coach, the Modified Mk1 coaches used along with D1733 for the demonstration runs (new logo and corporate image, Intercity services, etc.), the early style Mk2 coaches built in 1964, and the later style Mk2 coaches. Seeing as the XP64 train was full of new things back in the day, such as new interiors and new exterior, the coaches were essentially the prototypes for the Mk2 coach, but what made the coaches unique other than the interior and exterior? Were they used with regular Mk1 and Mk2 coaches in service? Are there any pictures of the coaches on the demonstration run or in regular service?

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Kameran/mbv67

Google revealed the following. Sadly there appear to be very few useful images of the coaching stock but there are facts to be gleaned from the following. Perhaps a more worthy train geek will be able to supply some more useful information.

http://www.railwaysarchive.co.uk/docsummary.php?docID=353

http://www.railwaysarchive.co.uk/docsummary.php?docID=353

http://en.wikipedia.org/wiki/British_Railways_Mark_1

http://www.telfordsteamrailway.co.uk/guidedtour/guidedtour.php?page=138&sound=0

http://www.railblue.com/rail_blue_history.htm

http://www.riviera-trains.co.uk/47853.htm

It seems that some are in preservation so this link may help you with further info.

http://martinimber.omegaowners.com/xp64.htm

Sorry I can't offer any more.