The label on the bottom of the case did not have any brand's or manufacturer's name, but it did have a FCC ID: HEU 292. FCC has a web page where you can search on FCC ID's, and it revealed the manufacturer as "Podworld" in Taiwan.
The keyboard is on the Deskthority Wiki as
Podworld 292, called so because of its manufacturer and model number. According to the FCC page, this was an OEM product, which means that it was resold under other brands (or not branded at all).
I would think that your keyboard could have been bundled with a PC from a small manufacturer, maybe a local store that sold their own PCs.
Previously known keyboards of this type did indeed have "KPT-like" switches (unknown unbranded switch similar to the KPT switch).
Some of these keyboards did have
double-shot moulded keycaps of high quality.