Hmmm,that is a very odd looking modification, to me the liner look's like it was an original French OTAN M-51 liner, but why is has these "chinstrap bales " retrofitted inside I do not know?
I like it's unique features ,It is a very clever design, a real mystery???
Ah you're right! It's like an OTAN! Never thought about this!
I see, i guess this is part of another Indonesian cloned helmet.
Hang on. I can see why Opex thinks it might be a mle51, as the profile is very similar, but I've just taken a look at all three types of sous-casque and none of them have anything like the rivet placement here. Apart from anything else all of them have an insignia grommet on the front, lacking on this object shown, and at least one centrally-placed rivet at the rear. Even if this was something modified from a mle 51 (or a Portuguese 964 even - given Poruguese presence on Timor) the shell should show evidence of filled holes. So, not convinved at the moment, here. Mind you I have no better ideas; I did check info on export versions of the mle51 but nothing like this.
I see, it's indeed a mysterious liner. Different with the France or Portugal. I guess this is indeed an indonesian cloned OTAN, made with different kind of part of liner suspension. Or maybe different construction from beginning? Or maybe Timorese version OTAN? So many possibilities.
With only part we have now, it will become an unsolved mystery. Like my firefighter helmet or medieval helmet.