Based on technical drawings from 1909. Each one is 2 in. dia and 4-1/2 in. long.
Are they retained by the shallow groove?
I’m absolutely riveted, but what tools are they!!?
Metal maracas \m/ .
Shep is correct. They are for doming the heads of iron rivets as you might see on a steam engine boiler or in old ironwork structures.
These were made in Australia by A. Goninan & Co Ltd.
I think the shank was retained with a clamp but I haven’t come across the drawings for the machine yet. I found a close up showing a similar rivet snap in use.
A little adhesive tape and she’ll float.