Strange GM 30 gask mask with Auer mark

[Deodaru]

Hello,
I must say then even I had more then hundreds GM in my hands I never come across piece like this, it is fresh find from old garage, but what is strange, then it was overpainted everywhere by some khaki colour with auer mark. I presumed it was used at some civil fabric ? Maybe at Auer itselves ?? Mask is 37, filter 38 and case 43 dated... Thanks for help