This is a small to medium klip and lock container containing simply a log book and pen
"This is a rather special cache that is being hidden to celebrate a future occasion. Something is happening on this spot onMay 23rd 2015 and if you can log this cache before then, you'll be a brilliant extra part of that occasion! The whole story will be revealed in the logbook in the cache itself. Please keep your logs vague - don't give the secret away online please!
It's a roadside cache and dash so let's get as many super duper geocacher messages in that logbook as we can by May 23rd! Thankyou :) "