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A rubber manhole cover, suitable for attaching to a top of a metal manhole lid, includes at least two bonded layers of rubber material of differing properties, including a bottom layer of a first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as

A rubber manhole cover, suitable for attaching to a top of a metal manhole lid, includes at least two bonded layers of rubber material of differing properties, including a bottom layer of a first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as a single unit.

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1. A manhole cover device, comprising: a bottom layer of rubber material, suitable for attaching to a top of a metal manhole lid, having a top surface; anda first top layer of vulcanized rubber material, having different material properties than the bottom layer, the top layer being affixed to the t

1. A manhole cover device, comprising: a bottom layer of rubber material, suitable for attaching to a top of a metal manhole lid, having a top surface; anda first top layer of vulcanized rubber material, having different material properties than the bottom layer, the top layer being affixed to the top surface of the bottom layer, the top and bottom layers functioning as a single unit. 2. A manhole cover device in accordance with claim 1, wherein the bottom layer is of recycled rubber material having a durometer of about 55-65, and the top layer is of Neoprene rubber, having a durometer of about 55-65. 3. A manhole cover device in accordance with claim 1, wherein the bottom layer has a thickness of from about ¼ to about 2½ inches, and the top layer has a thickness of from about ¼ to ½ inches. 4. A manhole cover device in accordance with claim 1, wherein the bottom and top layers are affixed via one of sag resistant adhesive, rubber-to-rubber adhesive, mechanical fasteners, and cement-type adhesives. 5. A manhole cover device in accordance with claim 1, further comprising an aperture, defined by sidewalls, extending through the top and bottom layers, for providing access to a portion of the manhole lid below. 6. A manhole cover device in accordance with claim 1, wherein the bottom layer is attachable to the top of the manhole lid by one of the mechanical fasteners and chemical adhesive. 7. A manhole cover device in accordance with claim 1, further comprising a second top layer of vulcanized rubber material, having a top surface, affixed to the top surface of the first top layer. 8. A manhole cover device in accordance with claim 1, further comprising indicia, associated with the top surface of the top layer. 9. A manhole cover device in accordance with claim 8, wherein the indicia comprise integral rubber inlays of contrasting appearance in the top layer. 10. A manhole cover device in accordance with claim 8, wherein the indicia are selected from the group consisting of alphanumeric characters, linguistic characters, ornamental designs, marks, logos and visual targets. 11. A manhole cover system, comprising: a manhole lid of metal, disposed below an elevation of surrounding pavement; anda cover, attached atop the manhole lid, comprising at least two bonded layers of rubber material of differing properties, the cover having an overall thickness sufficient to substantially match the elevation of the surrounding pavement. 12. A manhole cover system in accordance with claim 11, wherein the cover is larger than the manhole lid. 13. A manhole cover system in accordance with claim 12, wherein the two bonded layers of rubber material comprise a bottom layer of recycled rubber material having a durometer of about 55-65, and a top layer of Neoprene rubber, having a durometer of about 55-65. 14. A manhole cover system in accordance with claim 11, wherein the cover is attachable to the top of the manhole lid by one of mechanical fasteners and chemical adhesive. 15. A manhole cover system in accordance with claim 11, wherein the two bonded layers of rubber material comprise a top layer, and further comprising indicia, associated with the top layer. 16. A manhole cover system in accordance with claim 15, wherein the indicia comprise integral rubber inlays of contrasting appearance in the top layer. 17. A rubber manhole cover, suitable for attaching to a top of a metal manhole lid, comprising: at least two bonded layers of rubber material of differing properties, including a bottom layer of first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as a single unit. 18. A manhole cover device in accordance with claim 17, wherein the bottom layer is of recycled rubber material having a durometer of about 55-65 and a thickness of from about ¼ to 2½ inches, and the top layer is of Neoprene rubber, having a durometer of from about 55-65 and a thickness of from about ¼ to ½ inch. 19. A manhole cover device in accordance with claim 17, further comprising a third layer of rubber material, affixed atop the top layer. 20. A manhole cover device in accordance with claim 17, further comprising indicia of rubber material integrally inlaid in the top layer.