Identical to the Teledyne-Post Versalog, and all the raving i do about that one applies to this one, as well. I like this one better, though, because it was used. It belonged to the estimable Jim Rowland, a2b music demigod, rocket scientist, and all-around shady character. i like used slide rules, perhaps to an unhealthy extent for a collector. it's nice to know that the rule was actually used by a human being, rather than having just sat on a store shelf. i'm not sure why, but it is.