A surviving first rate belongs in a museum

If a fully functional Nelson-era first rate appeared at Chatham, would it be used or preserved?

It would be preserved as a museum ship at Chatham, not returned to operational service.

An uncrewed Age of Sail warship would properly be described as in ordinary rather than commissioned, because commissioning implied a crew and preparation for sea. A complete first rate appearing in the Medway would have exceptional historical value and almost no modern combat utility. Chatham Historic Dockyard would probably secure the ship immediately and build accommodation if no berth were ready. Its arrival would draw a clear line between commissioning, reserve status, and preservation.