Flottorp prop - original application?

[hangarbumdotcom]

Any idea what the original application was for this prop?

Doesn't fit a Lycoming, supposedly.

[Dave]

Any markings on it?

My first impression is that the bolt holes are larger than usual and that it may be for an airboat. It's also left hand rotation, which would be unusual for the common aircraft engines that size.

[MWP_Lamar]

Maybe it's a distortion of the photo but it also seems to be of too small a diameter to be an aircraft prop. I'll be interested to learn of any markings, too

Lamar