Does it have the name Hong Yeng printed anywhere on it? There are lots of variations of these pumps floating around online. Hong Yeng and Tuxing are the main distributors but there is a lot of unbranded models with slightly different specifications. I gather that they are all made in the same factory. The rust or staining appears that something has been spilled on it, probably in storage, does the box have any water staining on it? I would run it and check for leaks before loosening any joints unless something is clearly cross threaded. If it is, contact the supplier and work something out.