This is a gadget cache and everything you need will be supplied at the cache. Please leave everything as you found it. Do not lock the little box inside the cache where the log book is. Others will need to use that to figure their way into the log book and if its locked inside it will be impossible for anyone to access the logbook
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The number 9789 will be important to you but no, that's not the lock combination. However if you were in Australia you are golden. Once figured out dial in the numbers on the combination lock then push in on the lock to release it. When finished don't forget to close the lock and scramble the numbers.