Standard-issue simple Mannheim rule. As with most low-end K&E's, there's nothing particularly special about the rule, but it feels like it's well-built anyway. The top plastic bar on the cursor on this one is kinda falling apart. I once hear someone refer to this as "K&E Rotting Cursor Syndrome". It seems fairly common. It's possible K&E used celluloid in their early cursors, and it didn't stand up really well. Either that, or people kept getting frustrated with the word problems and were beating their slide rules on the desk.