- A pen with a clear casing
Open the pen up. Carefully roll a logsheet around the ink holder and slide the whole setup back into the pen. Make sure the logsheet is positioned so it is visible through the clear part of the pen casing. Then seal it back up.
Why leave the ink part inside? Why not? You can quite honestly say that you don't need to bring a pen to the cache, even if it is a micro.
This is a quick, cheap micro cache design. Make sure you have some spares for future maintenance and have fun as people log their surprise at this different design.