Girling do not advise splitting these calipers (not single casting TR3 type). However, when you have split them and realized you shouldn't have, you will need an 'O' ring to put them back together.
These seals are as close as we can get to the original, however, as Girling offer no information on them we cannot guarantee their fitness for purpose. In other words, use them at your own risk! Calipers are however available on an exchange basis, please use original numbers with an 'EX' suffix.