I do not collect Dutch helmets and my knowledge on these is limited and possibly wrong, but I know there are two models of this type/shape: M1927 and M1934. The M1934 being of slightly different (green) colour and curved shape than the M1927. Your helmet apparently has the shape of the model of 1934.
To my knowledge the Dutch Army helmets always were of an olive green colour and they had a (blackened) copper badge with a Dutch lion on the front. I have always believed the black ones, without the badge, would have been police, or (company/industrial) firebrigade, or civil defence, at least not Army. I know that for instance the company firebrigade of our former national telephone company PTT (for post, telegraph and telephone) had black helmets without the copper plate/badge, but with the letters PTT painted in white on the front, probably post war.
There is an interesting website, unfortunately in Dutch, on Dutch military uniforms and equipment from WW2 (limited to 1939/1940). What´s nice is that this website has some "interactive" uniforms. You can click on certain parts of the uniform/equipment and see more detailed pictures:
http://www.leger1939-1940.nl/Uniform/start_uniform.htm
Maybe someone with more knowledge on Dutch Army helmets can chime in here, and correct me where I am wrong..