Short Knuckleduster flying boat - photos

Short Knuckleduster flying boat from the 1930s. Only one was built.

https://diqn32j8nouaz.cloudfront.net...2_fullsize.jpg

https://diqn32j8nouaz.cloudfront.net...1_fullsize.jpg

https://diqn32j8nouaz.cloudfront.net...r_fullsize.jpg


Previously:

https://www.homemadetools.net/forum/...236#post211301
https://www.homemadetools.net/forum/...914#post194632
https://www.homemadetools.net/forum/...653#post186166

Can someone explain the "knuckleduster" reference? I don't see any feature of the aircraft that evokes my vision of that device.

A little more info is here, but not a good explanation. Short Knuckleduster - Wikipedia