If you are at GZ, you will have found a brass plaque on a large rock.
Thomas Drew was in fact a convict found guilty in England of horse stealing in 1831 and transported to Van Diemens Land for life. By "Ticket of Leave" he was in the cartage business in Launceston during the 1830's. By 1840 he had bought the 25 ton "Waterwitch" and used it to service the timber trade between the NW Coast and L'ton. He secured leases for the best timber inland from the Don River and shipped to Adelaide. Remains of one of the wharfs can be seen here. In 1841 he leased 640 acres of Crown Land on the west side of the Don River.
Drew was granted a full a full pardon in 1842 (a suitable reward for capturing two bushrangers at the Forth River), and allowed to purchase his 640 acres for 384 Pounds. Thos. Drew amassed a fortune when other pioneers were struggling merely to survive. He built a fine house on the west bank of the Don, overlooking the Heads.
The cache recognises a visible reminder of the past ---- gnarled old tall English trees near Thos. Drew's house site.
Cache is a container within a container within a container. NO pencil, no room for swaps.