This probably sounds really silly, but I want to get a second tea pot,
and the size of the pot I have now is ideal. I have an Arthur Wood
china teapot with a blackberry design that I got on a trip to Bermuda 15
years ago when I didn't even drink tea (I couldn't think of any other
souvenir to get and I liked the way it looked). Now that I am drinking
a couple of pots of tea a day using this teapot, I am concerned I'll
break it, so I'd like to get another and save this one for special
occasions.

So when determining capacity, how full do you fill the teapot? If
capacity is what fills it to the brim, then its a six cup, but if it is
to the level that I have read as optimum (more or less up to the point
where it starts to narrow again) then its a four cup. I just want to be
sure that what I order is the same size as what I have.