This picture comes from a souvenir booklet called "The Mine-Sweeper's Part in the Great Victory" published just after the First World War by the Belle Steamers. It has been lent to me by kind permission of Victoria Groom and comes from the collection of W E Groom, Victoria's Grandfather.
On 8 September 1917, in the Thames Estuary, Walton Belle found a "T" Type German mine. It was the only one of its type found in British waters and was commonly referred to as the Walton Belle Mine. Only one other mine of the type was found, and that was on the African Coast.