A lot of the connector suggest using a coin to screw them so I design a screw driver to fit a Canadian nickel (1.75mm tick). 

American nickel are slightly ticker (1.95mm) ticker you may need to scale the model up +/-10% (I did not test this as I dont have a US coin on hand). Heating the coin to insert it would probably also work.

The design is just secure enough so the coin will not fall down on its own but can be remove without much effort.