The only aircraft to be given 3 mission letters in the USN designation system, Hall Aluminum's PTBH.
The last design of Hall before they were acquired by Consolidated, was originally designed as the PTBH-1 to be fitted with Wright R1820 engines. A redesign for P&W R1830 engines led to a smaller design as the PTBH-2. Unfortunately I can find no details of the -1 version.
The aircraft performed well, but the Navy decided that the multiple roles of a large seaborne patrol torpedo bomber was no longer relevant, and so no production was ordered.