ROCK, United Kingdom, ??gt, completed London and Rochester, Frindsbury, 1961
1990 withdrawn from service - sold to private owners
A bit of a nebulous link to Dunston at Thorne simply because it is stated they designed this class of small Medway coasters.
See: http://www.hcmoorings.org/vessels-at-hcm/rock/
On the Thames - 15 July 2013: Ron