Dear Tombraider2
As Deceangi says, what you have stumbled across is a cache that we have in preparation - part of a series around Dunwich. Because some of the series are on land managed by the Forestry Commission, we are awaiting their approval for placing some of the caches before we can publish them on Geocaching.com. We hope to have the full series published shortly, but in the meantime, we'd be grateful if you could keep the precise location of the one you found to yourself.
Thanks,
Phil & Sue