This machine was completely different from Harrison's watch. It was a mahogany box of approximately that housed a movement that, though relatively simple, was close to the same size as Harrison's, with a balance of a similar diameter. The radical difference, however, was a newly designed escapement that featured a horizontally placed pivoted detent that allowed the balance to vibrate freely, except when impulsed by the escape wheel. The spiral balance spring also had a temperature compensation device similar to those in Arnold's watches, and based on Harrison's bimetallic strip of brass and steel. Arnold proposed manufacture of these timekeepers at 60 guineas each.