An enhanced accuracy and stability Bayard-Alpert gauge, now in general use for over five years, is reviewed. The philosophy of its design to control electron trajectories, location of ion generation, efficiency of ion collection, and maintenance of these characteristics is described with respect to computer simulation and its resultant gauge construction. Gauge sensitivity variation with pressure, from gauge to gauge, and over five years of operation is presented. A system for multi-gauge calibration is described as well as the system for maintaining the reference standards. Analyzing commercial use of this gauge in process environments over these five years has revealed knowledge relating to degradation of the function of each gauge electrode. Also analyzed are the process cycle requirements of quickly measuring base pressure under process conditions versus backfilling to pressures well above base pressure. Many of these concepts are generally applicable to most ionization gauges and will be discussed.