Simple horn question

Hi all - first post and I'm pretty new to horns. I have a dumb question that hopefully has a "rule of thumb" answer.

I just bought a B&C ME10 hf horn that's square with 90 X 60 coverage and is called a hyperbolic cosine. My question is, being a square horn, which way is horizontal and which way is vertical? I don't have any trouble with rectangular or round horns :D but I'm confused about which way to orient this one.

In one axis, the two parallel sides have a well defined, constantly changing curve with a very distinct tangency at 90 degrees just before the mouth. If I were to guess, I'd say these two sides have a hyperbolic cosine flare. The sides 90 degrees to them, are nearly straight for the last half of the horn out to the mouth. The curve is quite different and appears to be at ~60 degrees.

Is there some kind of educated guess that you can make when you see a horn like this based on the two different flares? I'm guessing that the sides with the curve that has the constantly changing profile (i.e. - most like what I would think a hyperbolic curve shoud look like) are the sides controlling the horizontal dispersion and should be oriented horizontally. The more-less straight sides at ~60 degrees, I would think should be controlling the vertical dispersion.

Am I confused beyond all hope? :) I have to believe that there's an easy answer to this.

Thanks,
Allan