I have been doing some research on clock escapements.  Turns out pendulum escapements aren't period by about 65 years.  Verge and foliot with a crown wheel where the pallets engage with opposite sides of the crown wheel are.  There are some verge and foiliot escapement designs which have 2 gears with pins that replace the crown wheel and the pallets both engage the top of these two pin gears.  I am looking to prove or disprove weather this type is also period.  Any help would be appreciated.  A simple search on firefox gives a great overview on wickipedia, and  www.youtube.com/watch?v=7HgAtCn3VUU shows the two pin-wheeled type.‎