Hello
I have just seen this site/ topic. I do naval research so can help.
NA 207 was a a Naval Ammunition Lighter built in 1943 by the MOWT. Transferred to the Admiralty post war she served at Chatham Dockyard as a Yard Craft under the Director of Armament Supply ( locally NASO) based on Upnor/ Lodge Hill armament depots. Not sure what use she had after 1984 when the dockyard closed but in 1990 when she was sold by by the MOD to DC Marine Gillingham,
in 1958 she became was part of the Port Auxiliary Service ( PAS). Ownership transferred from the Admiralty to the Ministry of Defence in 1964. In 1976 the PAS merged with the Royal Maritime Auxiliary Service (RMAS) under the latter name and as such would be renamed RMAS 207 (A)
Hope this helps
Regards
Michael