Recently found U-1435 from 1924 on a very interesting mount that I associate with "Pickelhaube" (https://en.wikipedia.org/wiki/Pickelhaube). The base is cast iron and heavy, it was mounted on top of the pole and fixed with screws or nails through four holes (next photo). Inside the insulator, the crumbling fabric residue that was used for the fitter's installation. This is the first time I see this type of "base" here in Norway, an interesting discovery. Thank you for looking.