Are those really ordinary pipe threading dies?
Yup, early dies were square because it's a lot easier for someone to cut a square chunk of plate and drill the holes in it than to make it some more complicated shape like circular or hexagonal. However, the square shape makes them a bit fragile..
The really unusual thing about the craigslist one is that it has it's set of inside reverse dies (aka taps). Most people have no clue what those are and loose them
The seller may be correct , the taps have no visible taper, they may be conduit dies....(which the telephone company would use occasionally...)
