most house numbered parts are common devices that a manufacturer contracts for (like the Sony MN2488 which is a 2SD2488 from sanken, made under contract for Sony), which still bears a portion of the original part number, or the equipment manufacturer contracts with the semi company to put a completely proprietary number on the device (such as the Peavey SJ6357 house number for an MJ13003). often in either case, the parts are preselected to meet a certain narrow specification that the equipment manufacturer wants. in the case of an op amp for instance, an equipment manufacturer may design something with an LM3886 power amp IC, but require the chips be preselected by TI to have ultra low thermal drift, which maybe 1 in 5 LM3886's meet the spec. they ask TI to mark them BFA886 as the part number. first of all, as a repair tech, you can't buy a BFA886 from TI or a distributor, you have to buy it from the amp mfg, (usually only available to warranty certified repair shops) and it's at least 5 times as expensive (because only 1 in 5 meet the spec)