When I bought it the price was $1.71, they’ve raised it to $2.45 by now.
It has a nice aluminium casing with screw on cap. Plastic sleeve with electronics and slot for battery inserted into it (image from review on GB):
IC has no markings on it.
Charging cut off: 4.21v
Discharging cut off: 3.03v
At about 3.2v the blue led will start flashing.
Power bank wont start charging if battery voltage is under 3.4v
Based on amp draw from USB it uses CC/CV charging, draining 0.7A/4.6V at the start and 0.05A near the cutoff.