Gary's Collection can be well-described as "substantial."
Among all the paper & plastic, special purpose rules/calculators are ones that compute impedance, given reactance & resistance, decibels vs. power ratio, parallel resistors/series capacitors, trans-mission line de-rating, coil turns vs. inductance, microwave path loss, etc., etc. Many of these were sold/given away by Andrew, IRC, Cornell-Dubilier, Allied Radio, Shure, Electro-Voice, ARRL, Decibel Products, Grass Valley Group, Ohmite, Hallicrafters, Burstein-Applebee, Nurad, Loral, Telonic, Belden, California Eastern Laboratories, General Electric, International Rectifier, Sprague, Sylvania, Cutler-Hammer, Scientific Atlanta, Wavelink, Broadcast Microwave Services, Operadio, Varian, Acrodyne, Prodelin, Antenna Specialists and Sitco - there is even a Smith Chart slide rule.