Provision may be made by regulations for further defining the principles on which the extent of disablement is to be assessed and such regulations may in particular direct that a prescribed loss of faculty shall be treated as resulting in a prescribed degree of disablement; and, in connection with any such direction, nothing in paragraph 1(c) above prevents the making of different provision, in the case of loss of faculty in or affecting hand or arm, for right-handed and for left-handed persons.