I have to report on 14-Sep-2011, the documents attached are the same as you received. But tell me where you posted at Headquarters or Plant?
And in every government department you always receive a offer letter first then after medical examination and security clearance (not in all departments) you get a joining order. So its a normal practice.

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A successful person is one who can lay a firm foundation with the bricks that other throw at him. (David Brinkley)