Doug, interesting find. I hadn't heard of the GanGuang so I did a bit of digging.
It seems that they were first produced in '83. The JG suggests that it was a commemorative model.
Here is a complete translation of the camera's spec's etc.
It is an auto translation and I haven't cleaned it up, but most is relatively understandable.
Ganguang JG304C: Gansu Optical Instrument Industrial Company in July 1983 trial success!
Brand: Kam Kwong, Ganguang, (formerly known as PHENIX).
Type: JG304C
Type: use 135 film, containing pop-up flash jump stand, electric eye metering, electronic program shutter, next to the axis head-up viewing of the 35mm automatic exposure camera.
Frame size: 24mm × 36mm
Features: It can be photo objects according to the brightness automatically determines the aperture value and shutter time, to achieve the camera's automatic exposure.
Shutter: Using Seiko (SEIKO) ESF-D849 electronic program shutter speed of 1 / 4 sec (aperture F2.8) -1/450 (aperture F17).
Aperture adjustment range: f2.8-f17
Metering mode: camera next to the outside with a CDS photocell type metering body photosensitive resistor CdS CdS average metering done outside the machine.
Metering range: Spot linkage range EV5-17 (ISO100), EV8.4 (F2.8, 1 / 45 sec) The following are a low-light tremor warning.
Photographic adjustment range: front of the lens has a manual adjustment rings DIN15-27 (ISO25 - 400), and automatic exposure system linkage.
Viewfinder: reverse Galilean type with light-style head-light frame viewfinder, parallax correction marks and shot at close range shot from the yellow icon, and a focal length of the linkage indicators show that the red LED light show exposure conditions and flash charge are shown.
Film Mode: Wrench type, Strip prepared to handle angle 30 ° operating angle of 140 °.
Total number of devices: Shun add style count.
Self-timer mode: mechanical self-timer, the delay time is about 8-12 seconds.
Lens: Focal Length 38MM, relative aperture 1:2.8, four three, coated lens, field of view angle of 59 degrees, short focal length greater depth of field before the focus group.
Filter Size: M46 × 0.75
Focus Mode: object distance adjustment lens ring, which have distance scales, and 5 away from the flag map, the shortest distance photography 0.8M, visual distance, experience, focus assessment.
Flash: Built-in pop-up flash Li jump GN10, (ISO100 / m), flash effective range 0.8-3.6 m, the back cover the scope of the table with flash photography. Manganese dioxide battery charging time is about 10 seconds, after charging, shooting light starts flashing red LED lights inside the viewfinder also will flash. Do not have time to reset. The machine has FM Flash Linkage, low brightness flash, aperture, and photography from the linkage, high brightness flash, can be used as auxiliary flash, small aperture priority.
Body: body, top cover, bottom cover with ABS precision engineering plastics and advanced surface coating technology, full black body, smooth surface, compact design, the body size of medium (130mm × 84mm × 55mm), Weight 330g (without batteries).
Power supply: 2 batteries, 5, (machine on the scope of a larger battery, manganese dioxide batteries, alkaline batteries and nickel-cadmium batteries can be used) the minimum operating voltage 2V (when the supply voltage lower than 1.9V, the shutter auto-lock).
Accessories: packing box, manual, maintenance card, certificate, leather holster, straps, plastic lens cap.
=================================
Copy of a person being copied by:
"GanGuang JG304C" and "Minolta HI-MATIC SD"
In addition to working on the difference between raw materials and also the relative diameter
"Sweet Light" JG304C relative aperture 1:2.8
Minolta HI-MATIC SD relative aperture 1:2.7
Country: China / Japan
The last bit is intriguing and, sure enough:

Photo from
www.collection-appareils.fr/minolta/images/minolta_himatic_SD.jpgGiven Minolta's investment in the Chinese camera industry, the GanGuang could well be a licenced copy made on old Minolta tooling rather than a counterfeit.
Phenix, BTW, is based in Jiangxi Province, in the south and a long way from Gansu Province, where the GanGuang appears to have come from.
The famous Phenix rangefinder was the 205, which started life as the Seagull 205.. I had one of the last ones made. A pretty camera, but fairly rough when compared to contemporary Japanese rangefinders.
here's a link back to the thread with a photo of my 205.
cameracollector.proboards.com/index.cgi?board=show&action=display&thread=4480The Chinese info comes from a JG304c users group in China.
www.douban.com/group/JG304C/