My experience with the flat bronze markers is that dirt gets on them and grass eventually grows over them. The next time I go to Vincennes, I need to take my trowel and dig the dirt off my grandparents marker before it obscures their names. It's been there about 30 years. Dirt and grass growing over the markers is a big problem with flat markers. No one, including those who run the city cemetery, can find the markers in the area near the highway (Fairview Cemetery) where my father's sisters are buried. They had small concrete plot numbers and wooden markers, but the concrete numbers are several inched below the grass, now. They've been there at least 80 years. Sharon Howell