... Interesting way of measuring and with 6, 7 and 8 obviously a design point!
It's an interesting, novel, and brilliant marketing and sales point, Frank. I wonder how many mathematicians have puzzled over this in the shop and then just had to buy a pair ("Sorry, Sir, we only sell them in pairs") so they could get them home and measure the angles, other dimensions, and the volume. My first reaction was that I couldn't remember such a special property of octahedrons.
It's those extra few sales that make you the profit.