What to do with this WW2 find

[Betonov]

Original colors are existant underneath, there are some clean spots where the army gray can be seen. I'll try to make a pic of it tommorow when I fiddle a little with the camera's ''insect zoom'' (as it says in the manual).
Chemistry should help me with this, what takes of lime and not anything else ?? If any of you know tell me. It wont be until march till I start work on this helmet, the garage is simply too cold so proper solutions can be found in ample time.

Lttle OT: Can you recommend a good read about the role of Slovenija in WW2? It often gets left out then talking about the war on the balkan and especially the year 45 seems to have been very interesting and intense . I read a little about when the papers here wrote about the mass graves in Mostec they found 3 weeks ago.

Can't think of any right now, but I'll PM you if I find anything