I discovered reference to this door spring in a correspondence between Sir Edward Filmer (3rd Bart) and his brother Beversham Filmer on the 13th of October 1748 via the National Archives online.
"Filmer Manuscripts. CORRESPONDENCE. Sir Edward Filmer (3rd Bart.). Letters from his brother, Beversham Filmer. From his brother, Beversham Filmer. About sending a door spring having a watch repaired and music he had left at East Sutton
Held by: Kent History and Library Centre Date: 13 October 1748 Reference: U120/C28/43"