Woerd’s Patent Regulators from #550,233 and #690,511.
By 
Around 1872, Waltham modified the original regulator design on the Model 1870 Crescent Street, adding another arm to distribute the force against the adjustment wheel more effectively and improve stability. The single-arm design was only fitted on the back key-wind/key-set movement while the double-arm design has been found on all variants.
