The MRC/WLC discrete cell reading-head technology steadily advanced over the years - starting with the temperamental Sylvania germanium-based 1N77B photodiodes [via 'through the sheet' mechanical shutter-gated transmitted light reading on the MRC Mod-I], through a succession of improvements: replacement of the unreliable mechanical slide shutter with a greatly improved rotary Ledex-solenoid operated shutter, to finally eliminating the mechanical shutter altogether by replacing the Sylvania photodiodes with silicon-based Texas Instruments 1N2175 photodiodes (no 'blinding' by direct light exposure between sheets, and no 'dark current' leakage), to yet later switching the primary mark-detection means from transmitted light to reflected light. Other novel designs used fiber-optics techniques (patented), rather than a bank of tungsten 'headlight bulbs', and/or high-wattage heat generating quartz-halogen tubular lamps. The culmination of this progress was the development of the so-called wafer head where a small module less than 0.100" thick contained a miniature phototransistor and two near-infrared (NIR) light-emitting diodes (LEDs) - a complete package for mark-detection in any given column on the test sheet. By varying the center to center spacing of the wafer modules across the 8.5" width of the scanned sheet, any mark-bubble spacing => than 0.100" could be easily accommodated, such as widely used MRC spacings of 0.102" and/or 0.127", or six/inch and/or eight/inch used by NCS, IBM, and others. The Archival DVD Folder, as named above, contains a JPEG-Image scan of an MRC/WLC wafer detector assembly (before sealing with epoxy), and several JPEG images of a typical reading head incorporating the wafers, and also an MS Word File 1970s_Wafer Reading Head_ORG.doc which describes the assembly. This JVM Accession Item also includes a hard-copy printout of the MS Word file with an actual specimen of the wafer, and the donation of a complete reading-head assembly