Attestation document, I presume they are at Kew. If there, you know the Regiment, so should have no problem. As he went to pension and was a Chelsea Pensioner he should have a personal service record also.
Attestation would be by an NCO, named, date of attestation, place of birth, age, occupation, height, complexion, eyes colour, hair colour, face shape.
Personal records were detailed.
The Regiment was in the Low Countries 1793-1796 (French Revolutionary War), 1809-1814 Spain and France, also at Waterloo 1815.
The official title at this period was 16th (The Queens) Regiment of (Light) Dragoons.
Roger