It's pretty common for keyboards to have no branding at all, or for there to be no indications of who actually made it. Frequently, keyboards are branded as the customer, not the OEM. For example, my two Tulip keyboards are made by Monterey and SMK, but they have Tulip's own model numbers and logo. The former does not say "Monterey" anywhere (I only IDed the OEM when someone posted a photo here of a stock Monterey K101), and the latter has SMK written on the PCB.
Sometimes the same product is registered to more than one OEM, and you can't tell where it really originated. The ETC PowerGlide 105 was registered by Commtron Corporation in the US, (not ETC) while it was probably made by Ortek in Taiwan or some factory they hired. The SIIG and Micro Warehouse branded versions were also registered by Commtron, although some Micro Warehouse production runs had an FCC ID registered by Wentek Technology Inc in the US. Mine has an 'O' for Ortek key, and Ortek's name does appear on the PCB.
The Monterey K101 was registered with the FCC by Monterey, as were the K104W and K108/K108W (the 'W' models are not confirmed to exist). In between these, K102, K103 and K104 (not K104W) were registered with the FCC by Keytech, whoever they were.
Some modern Dell keyboards have recognisable details (e.g. SK models from Silitek and RT models that say NMB on them) but most of them have no recognisable manufacturer details anywhere inside or outside. The OEM is often a secret. You would also find keyboards that didn't even have OEM customer branding — mystery keyboards!
A few companies like IBM actually made their own keyboards! That was rare, though. The term "Bigfoot" that is applied to Alps switches is a mistake: "Bigfoot" refers to the Alps standard keyboard platform used for a lot of keyboards, such as the Bull we saw here recently. (The SGI Granite looks the same, but I don't know that it's not made by Silitek, the same as later Dell AT10X(W) keyboards.)