This is an excellent 3D viewer for Stereo Realist format slides. No cracks, no chips, no corrosion, smooth interocular and focus controls, steady unflickering illumination and doublet lenses that are clear, clean and sharp for undistorted viewing. But while this viewer is a great user, it's a poor collectible. Why? That's because it is missing the Revere logo on the trapezoidal lamp activation button.