DD Police helmet, markings question?

[Wartime Collectables]

I've seen reference to 'dome markings' but no clue what there meaning is. Sorry I can't seem to get a better picture. Aso what is the big PO liner marking next to the the vets capture date note? THANKS

[Wartime Collectables]

Thanks in advance for sharing your knowledge!

[Kesselberg]

That is a beautiful helmet. Its a Ministry of War Production inspection stamp.

[helmuthunter]

Very nice example indeed!

[Wartime Collectables]

Thank you gents! And the PO 1940 liner marking?

[billbert]

That stamp I believe is a property or acceptance stamp for police items..seen on helmets hats and uniforms..and probably most all items..Billbert

[Kesselberg]

I am not sure what the liner stamp is.