The mechanical stage of the Nelson-Curties No 1 and No 2 microscopes used a modified from of a design proposed by Mayall. In Mayall's original design, left, slide movement in both directions was promulgated by a mechanism that simply pushed the slide around on a top plate without the use of two moving plates. The Nelson design anticipates the modern mechanical stage in that this mechanism is used in one direction, but a moving plate (or in this case a frame) is moved in the other. Originally, two different types were supplied with Nelson models, one with concentric controls, like the original Mayall design, the other with separate controls. Both Nelson No 2 microscopes in this collection have separate controls for the two axes. By the time the Nelson No 1 came out, Nelson produced a more sophisticated mechanical stage with concentric controls for the Nelson-Curties No 1a microscope. The later version of the Nelson No 2 has two moveable bars to hold the slide; the earlier version, with more options, uses stage clips.