A long time ago I was involved with licensing databases (of new and used car price books-- e.g. Edmunds, Kelley Blue Book, etc.) They had the custom of salting the data with a few deliberate errors so that in the event of an infringement suit, they could prove that their data had been copied by the infringer, rather than independently created. I can't say whether the same purpose applies to schematics, but it just might be. Brad To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Message-ID: <459D59AD.3087.22DE923 at cclist.sydex.com> Content-Type: text/plain; charset=US-ASCII To be certain, some errors/additions are deliberate; Rand McNally generally sprikles a few non-existent landmarks in their maps; Google satellite maps have "watermarks" that can be very confusing. I spied what looked to be clearing on some of my forested land and hiked to the very spot and found--trees, just like everywhere else. It took some conferring with a USGS employee to discover that what I thought was a clearing was a rather subtle watermark (viewed in just the right way, you can make out a "Go".