Handsome antique lumber caliper for measuring size and length of logs or rough timber. Made of beautiful wood and brass with clear markings and the name "William Greenleaf", the well known manufacturer from New Hampshire. More detailed photos available.
The spiked wheel was for measuring the length of the log within six inches. The measurement is started with point of the black, lead weighted spike (so gravity would force it to be the starting point) and the wheel is moved along the length of the log.