----------------------------Original message---------------------------- This weekend, a friend who is technical coordinator for the geology department at a small University showed me a plaster relief model from the late 19th century of the Four Corners area that he found in the basement of the geology labs. It was evidently prepared for (or under the auspices of) the USGS. (Back in those "halcyon" days when John Wesley Powell was director...his name was on it). I'd like to find appropriate information on the proper way to restore this to it's original state. Does anyone have any references for such work? Thanks,