There is a fairly good writeup on various slide rule types and scales, on http://www.quadibloc.com/math/slrint.htm http://www.quadibloc.com/math/slrint.htm (the

There is a fairly good writeup on various slide rule types and scales, on http://www.quadibloc.com/math/slrint.htm http://www.quadibloc.com/math/slrint.htm (the rest of this guy's site is worth exploring on its own too, there seems to be a huge dump of various bits of knowledge on it).