At one time, I had a problem with one of the HP's MFPs. While I was in the country, in the fresh air, the idea came to me to call HP technical support and ask about this problem, maybe what advice would be given. Here is only one problem - in the technical support with me inextricably refused to communicate until I call them the serial number of the device. I did not have a clear issue at hand, so I used the smartphone to Google.Images and there found a clear photo of the same model and its rear wall with a shield, where I took not know who the serial belongs to and dictated to the TP operator. Immediately received advice and advice on troubleshooting.