This is the ratchet model from 507 Mechanical Movements: http://507movements.com/mm_075.html
You will need a 3/8" dowel and 2x 1" #6 sheet metal screws. It is best to assemble everything on the dowel, pilot drill through handle and moving pawls hole, screw screws in, and cut the dowel ends flush.
Some filing will be necessary to get the stop pawl to fit.
See my blog post about this here: http://artofrandomness.net/blogs/matts-blog/ratchet-model-maychanisms-1/