This part is an Osterrath air filter assembly, which is used for air intake systems. The filter element can be used to remove dust and other contaminants from the incoming air stream, which helps to improve the performance of the engine. The filter assembly includes an inner and outer stage filter, and a safety guard. The part number refers to the dimension of the filter assembly. The first two numbers (61) indicate the filter depth, the last two numbers (1560) indicate the height of the filter, and the middle two numbers (11) indicate the width of the filter assembly. The final two numbers (0031) refer to the type of filter element used.