I think they are quite rare, is there a slot on the front for a cap badge? The rumour at the time was Vickers used sub-standard steel making the helmets brittle so not a lot of use as intended

the Free State (as was) was quite embarrassed about how ‘Germanic’ the Defence force looked at one time and had thousands squashed and used as landfill. The UK government I believe shipped off a load of ‘Tommy’ helmets as replacements.