It is a National Defense brand bicycle.

Defense brand bicycles are a type of bicycle produced by Qingdao Bicycle Factory. They are divided into heavy-duty National Defense brand bicycles or ordinary National Defense brand bicycles, commonly known as "Big Defense" and "Small Defense". The rear wheel adopts a reverse wheel brake, which can be braked by gently tilting backward. The front wheel adopts a lever brake, which has strong braking force. Production began in 1952 and was changed to the Golden Deer brand bicycle in 1967.

Extended information

Features:

The handlebar has a shallow "U" shape, a thick beam, and a thick cowhide base, which is strong and sturdy. The rear seat is square, making it very convenient to carry people and things. But the car is very heavy, half as heavy as the car. The most different thing from a car is that the brake is not on the handle, but on the pedal. As long as the pedal is tilted back, the car will brake immediately, which is especially easy to use. Another main feature is the "three major components and one suspension" (large flywheel, large chainring, large buckle chain, and suspension spring saddle).

Baidu Encyclopedia-National Defense Brand Bicycle