The cessation of his pension is shown as due to his death on 21 Sep 1853 and his age was then recorded as 76.
This document is proof positive that this Orlando Hallett was the one who died at Plymouth in 1853 and the one who became a Naval Pensioner in 1815 after 15yrs service as a Marine.
The apparent anomaly of a Naval Pensioner appearing in 1842-52 British Army Records is explained by the following heading before Section 1 and after Section V11 to these monthly papers relating to 1st Plymouth District.
"Monthly return of Transfers, Casualties etc, which have taken place among Out-Patients of Chelsea and Greenwich Hospitals, and those belonging to the East India Company in 1st Plymouth District, from 1st to 30th Sep 1853." As a former Marine, Orlando became an Out-Patient of Greenwich Hospital.
This record is numbered in the WO22 series at The National Archives, which signifies Army Records and undoubtedly the Army became involved in some capacity with the administration of Naval Pensions around 1845, as the last details I had previously found of pension payments to Orlando Hallett and others in Naval Records was a payment on 9/4/1845 with gaps for later payments in 1845 and 1846 left blank. I had assumed a new format for such payments had probably started but had failed to find any later pension payments of theirs, even though they must have continued.
I had no idea the Army had ever become involved with Naval Pensions for a time but you learn something new every day.
On the assumption that Orlando Hallett is one of your direct ancestors and, in case you do not already know, the marriage entries for his sons, Walter, 28/10/1939: Samuel, 8/4/1844: Edmund, 10/9/1854, are online and show Orlando as their father.