Ok Dave,
What the heck am I looking at. At first I thought somebody had forgot to clean all the chips (swarf) of the part. Then I noticed numbers and what appears to be the beginings of holes. 
Oh ,and very big, by the looks of it, well at least quite heavy.
Bernd
Bernd, as know it all Boggy says, it`s a rock bit. Minus it`s carbide inserts....
Oh look..... Here`s another!

The numbers are gradings by the inspection dept.
Dependant on size of bit, nominal sizes 10, 12, 14, 16, 18, 20, 22mm. Each size with 5 available grades (coloured), in 5 micron increments.
The holes were drilled to an accuracy of 3 micron........ Mostly!

The bit was then heated and the buttons driven in.
I really showed that pic for the splining, with side & face cutter.
You might like to see the sort of thing we machined...... From solid......
Overburden drilling parts.



Funny...... I don`t miss working at all.....
