Beijing Watch Factory
Shuangling

model is called Double Rhomb
17 jewel · day date
Case diameter: 35mm (excluding handle)
Case thickness: 10.3mm
Acrylic crystal
It was produced in the late 1980s 

The black coating is new and the crystal looks to be new

the watch  movement looks to be in very good condition

 +15 seconds per day and a 4.0ms beat error

setting the day and date is interesting, you rotate the time till one clicks over and then move back and fore around this point to advance, then follow for the other dial

The green dot markers ar paint and not lume

the case back is very worn indicating a local use, the strap is black leather and is adequate quality

lug width is 18mm