For those who dont know, pinball machine serial numbers for all of your machines can be kept on the IPDB site and recorded.example below of front serial pagehttp://www.ipsnd.net/View.aspx?id=4443

I notice the numbers growing in the IPDB however, the entries are still way below what you would expect. I think it is an excellent idea to have a collection of serial number world wide and to see in which countries all the pinnies reside.