After solving the su do ku :
Subtract 970702210 from North west to South east
Subtract 212232355 from South west to North east
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Above is the original cache description; below is newer supplemental information:
Thanks are due to "Grampa Cardigan" as the original hider of this classic cache.
The solid-rock-seekers (who were the first finders of the cache on 9 November 2006) adopted the cache in 2022 to maintain it for future generations of cachers to enjoy.
To aid future finders, a solution checker was added to the cache page.