(AR) A used part pulled from an aircraft. It may be fully operational, repairable, or beyond economical repair. Generally, these items need to be sent to a qualified MRO for testing and/or repair. These units rarely come with manufacturer certificates or airworthiness documentation.
(SV) A used part that has been tested in accordance with OEM specifications. Typically comes with a FAA 8130 airworthiness certificate.
(RP) Usually a used Serviceable part that required some repair to qualify for an FAA 8130. Likely comes with a teardown sheet detailing what was done.
(OH) A used part that has been thoroughly overhauled. May or may not have been cosmetically renewed.
(FN) Is a New Part. Generally shipped direct from the manufacturer and is less than 2 years old. Comes with manufacturer certificate(s).
(NE) Is a New Part. May have traded hands with distribution. May be more than 2 years old but has not been installed or used. Usually comes with manufacturer certificates.
(NS) Is a New Part sold to one party (airline) then sold to another (distributor) and is now available for purchase. It is a new part, just not being sold by the manufacturer or first tier distributor. Check to see if manufacturer certificates are available.