The early design and test results have been previously reported. During the subsequent operation of "D20" the accelerator prototype dipole has provided both additional and more detailed data as to its characteristics and performance. D20's use as a test facility for high field critical current measurements has provided operational experience and history pertaining to accelerator required characteristics. There has been recently obtained data related to field quality, operational reproducibility and reliability, which will be presented. This prototype "D20" has attained the highest magnetic field of any accelerator prototype dipole constructed and tested to date. The magnet has continued to operate routinely.