The HPNL's "B" collection is strongest in Western philosophy, and weakest in non-Western. The collection is especially strong in modern, German philosophers.
The BQ subclass for Buddhism was only introduced in 1972, and codified in the 1984 edition of the classification scheme. Before 1972, books on Buddhism were classed in BL1400-1485. We do not use the older call number range in the HPNL, but if you are browsing in the Main Stacks, or in the Library Catalog, bear in mind that older imprints will be classed in that now-obsolete range (BL1400-1485).