Information graciously supplied through URW, via Vincent Ertner: Each URW font has an assigned font number. The last character describes the size or purpose of the font, as the design of the font is optimized accordingly:
X000000E
X000000T
X000000D
X000000P
X000000M
X000000L
X000000I
The urw.map file has abbreviations for URW fonts.
uagd8a URWGothicL-Demi a010015l uagdo8a URWGothicL-DemiObli a010035l uagk8a URWGothicL-Book a010013l uagko8a URWGothicL-BookObli a010033l ubkd8a URWBookmanL-DemiBold b018015l ubkdi8a URWBookmanL-DemiBoldItal b018035l ubkl8a URWBookmanL-Ligh b018012l ubkli8a URWBookmanL-LighItal b018032l ucrb8a NimbusMonL-Bold n022004l ucrbo8a NimbusMonL-BoldObli n022024l ucrr8a NimbusMonL-Regu n022003l ucrro8a NimbusMonL-ReguObli n022023l uhvb8a NimbusSanL-Bold n019004l uhvb8ac NimbusSanL-BoldCond n019044l uhvbo8a NimbusSanL-BoldItal n019024l uhvbo8ac NimbusSanL-BoldCondItal n019064l uhvr8a NimbusSanL-Regu n019003l uhvr8ac NimbusSanL-ReguCond n019043l uhvro8a NimbusSanL-ReguItal n019023l uhvro8ac NimbusSanL-ReguCondItal n019063l uncb8a CenturySchL-Bold c059016l uncbi8a CenturySchL-BoldItal c059036l uncr8a CenturySchL-Roma c059013l uncri8a CenturySchL-Ital c059033l uplb8a URWPalladioL-Bold p052004l uplbi8a URWPalladioL-BoldItal p052024l uplr8a URWPalladioL-Roma p052003l uplri8a URWPalladioL-Ital p052023l usyr StandardSymL s050000l utmb8a NimbusRomNo9L-Medi n021004l utmbi8a NimbusRomNo9L-MediItal n021024l utmr8a NimbusRomNo9L-Regu n021003l utmri8a NimbusRomNo9L-ReguItal n021023l uzcmi8a URWChanceryL-MediItal z003034l uzdr Dingbats d050000l