Just going from the pictures then they are different when it comes to the pliers.SGT: Non-folding pliersSGT-Plus: Fold out pliers
Karl sent me this document from which I made the screenshots in the first post:http://www.docstoc.com/do...ientific-Glass-TechnologyOn the 7th page of it there's a list of all available tools and variations. They have an extended tool kit and standard replacement tool kit listed there. I think the empty layer could be for those tools.