Mk3 Turtle helmet stamped Z58 ?

[Bavarian]

Hello
I post this helmet again because Finally I found the heatnumber
I wondering me why it was stamped Only Z 58 and not BMB or something
There was no date on the shell
Is it a real MK3 or a other helmettype
It is postwar refurbished
What means Z 58
I need your help to this heatnumber

Best regards
Bavarian

[Composite]

its not a "heat number" - it's a metal batch number - and the makers stamp and the date should be with it - these are easier to see on smooth interiors. It looks like a Mk3 to me although the liner hole looks enlarged on the first pic.

it always helps if you ask nicely - "please"....Bitte etc