Most doors have a sticker or stamping that says "Listed Door Close 149A." This stamp or sticker is the UL insignia. UL stands for Underwriters Laboratory, which was established in 1894 and tests many different products for safety purposes.
Most doors will have the manufacturer's name on the door. Also, look for model numbers, hole spacing of hydraulic cylinders, the way the door is mounted and which way the door handle faces. Most of this information can be located on the inner portion of the door.Learn more about Manufacturing