The triangular ones are sales used for drawing and measuring plans in standard scales. There are engineering scales and Architectural scales, which are very different.

The Engineering scales use scales of 1:10, 1:20, 1:30, 1:40, 1:50, and 1:60 scales, and are usually used for drawing at a scale like "1 inch= 50 feet". They're generally used for civil engineering, so the plans show a larger area.

Architectural scales have scales based on fractional inches and are weirder, with units that are 1.5", 1", 1/2", 3/8", 3/16", and 1/8". They're used for larger scale drawing like buildings rather than the site-level drawing from the engineers.

I've seen that! I don't think the bulk justifies the 6 sides unless you take nerd cred into account.