National archives has an entry which can be downloaded which may be what you have. He would have joined up locally, and then been sent wherever the authorities decided. Would suggest you try googling the a40th and 70th REgt and see what you find. Good luck. Because he had served 21 years, and presumably was a good soldier, no black marks, he would be entitled to a pension, which is probably what the "proper object of His majesty's bounty etc means.