The pen is mightier than the sword

What kind of writing implement could have done this???

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Visited three museums today: tank museum, jail museum and and a medieval castle. Very interesting day as a whole. Unfortunately on the way home my car broke down - thick cloud of smoke came out from the exhaust pipe after which the engine didnt run so well. I quickly found a place to park. When I opened the hood and started the engine again, smoke came from the engine too - apparently oil leaking somewhere. Taxi ride home then...

I try hard not to think about how expensive this might be... =(