This is a very high quality grade 10 ball. The lower the grade number the better the accuracy and surface finish of the ball. Typically available steel balls are grade 100.

Replace your worn ball and get lower noise.

The second photo shows a microscope image of an original steel ball removed from a good used TD124 MK1. The wear on the original ball is very hard to see with the naked eye and most people don't realise just how badly worn the ball gets from normal use. Under high magnification multiple sets of score marks are clearly visible on the ball's surface! The pictured example is absolutely typical and not a particularly severe case.

The original steel ball is retained by a brass cap which is held in place with four crimps. Carefully pry off the brass cap with a sharp blade and discard it.

G10 steel and G5 ceramic bearings are available in my other listings.

Please check my other listings for more high quality parts for your TD124 bearing rebuild including nylatron thrust plates and the correct specification of oil.