Finally here is the link to the video.
The section on the 1540 wheellock starts ca. 14 seconds after the beginning of the video:
http://www.youtube.com/watch?v=NSyxpvIZXxY
That guy, Iain, is stating a few things that are incorrect.
E.g., he actually touches the wheel, encircling it and at the same saying that it is missing - which of course is complete rubbish!
I thought the Rotunda had personnel that at least knew what they were talking about ...
Best,
Michael