The 55T rifles that I have are all fitted with the early 11mm scope rails and need the HW 11mm rear dioptre to fit them.
Most 55T rifles still have their WH dioptre sites attached as target rifles are generally well looked after and kept complete.
The only HW55T rifles that I have had that have not been in top condition are those that have been "butchered" by adding over-powered springs and scopes and this destroys the smooth shooting characteristic that makes the rifle as good as it is.
Fortunately there are very few like this about and they are best avoided. IMHO.
Rossendale Target Shooting Club. Every Tuesday and Thursday evening 7 - 10pm.