I have restored a number of telephones of late with induction coil No24 or No27 having been removed.
Please make sure when you are buying a restored telephone that the induction coil has not been removed. Although the telephone will work its speech quality may be very poor. This is a practice that I would never recommend and can only imagine the sellers believe it is easier to fit the little internal bell inside. I love these little mechanical bells and they can be fitted with a small bracket and so no damage is done to the base of the telephone and can be removed if wished with no sign it was ever there. The bracket also lines it up perfectly in position so as not to hit anything inside. I have seen these pop riveted inside on many occasions. I should note that this bell is ideal if you wish to use your telephone without a bell set either fixed to the base or the wall and will give a nice mechanical sound and not too loud if being used as a bedroom telephone. I offer this as a free option.