The Mercury stuff all comes from a factory in Shanghai which is a prolific producer of consumer electronic products as well as some military items. Mercury products would be similar to brand names such as Zenith or Magnavox back in the '60's. So evidently it's not exactly a series of sets like the British Larkspur but rather a line of products from a single manufacturer, which also designs them. There is also a radio identified as the Mercury Walk Radio. It is powered by 11 D cell batteries.
All controls are on the top panel.
It tunes 45 to 50. The top panel controls are located under a cover held closed by spring clamps such as found on U.S. military radios. Main tuning control had a lock down lever. Other covered controls were a two position switch and a rotating dial, numbered 1 to 10, presumably a volume control. Two more controls are adjustable by screwdriver and there is a socket for plugging something in, presumably a calibration device.