So what if it is not a mail ship and not a military ship?
AHT Anchor Handling Tug
AHTS Anchor Handling Tug Supply vessel
CRV Coastal Research Vessel
C/F Car Ferry
CS Cable Ship
DB Derrick Barge
DEPV Diesel Electric Paddle Vessel
DLB Derrick Lay Barge
DCV Deepwater Construction Vessel
DSV Diving Support Vessel/ Deep Submergence Vehicle
DV Dead vessel
ERRV Emergency Response Rescue Vessel[citation needed]
FPSO Floating Production, Storage and Offloading Vessel
FPV Free Piston Vessel
FPV Fishery Patrol Vessel
FT Factory Stern Trawler
FV Fishing Vessel
GTS Gas Turbine Ship
HLV Heavy lift vessel
HSC High Speed Craft
HSF High Speed Ferry
HTV Heavy Transport Vessel
IRV International Research Vessel
ISV International Space Vehicle
LB Liftboat
LNG/C Liquefied natural gas carrier
LPG/C Liquefied petroleum gas carrier
MF Motor Ferry
MS (M/S) Motor Ship (interchangeable with MV)
MSV Multipurpose support/supply vessel
MSY Motor Sailing Yacht
MT Motor Tanker
MV (M/V) Motor Vessel (interchangeable with MS)
MY Motor Yacht
nb Narrowboat
NRV NATO Research Vessel
NS Nuclear Ship
OSV Offshore Supply Vessel
PS Paddle Steamer
PSV Platform Supply Vessel
RV Research Vessel
RMS Royal Mail Ship or Royal Mail Steamer
SB Sailing Barge
SS (S/S) Steamship (with screw propellers, can be either coal- or oil-fired)
SSCV Semi-Submersible Crane Vessel
SSV Sailing School Vessel, Submarine and Special Warfare Support Vessel
ST Steam Tug
STS Sail Training Ship
STV Sail Training Vessel or Steam Turbine Vessel
SV Sailing Vessel
SY Sailing Yacht or Steam Yacht
TEV Turbine Electric Vessel
TIV Turbine Installation Vessel
TS Training Ship
TSS Turbine Steam Ship or Twin Screw Steamer
TV Training vessel