What did I find in my sump?

[festy]

I just finished dropping the sump off my '77 GTV, and I found a couple of unexpected parts inside 

I was expecting to find the broken camshaft vernier lock bolt, when I snapped a cam a while back I guessed it ended up in the sump but the other two bits were a bit of a surprise.

The woodruff key is for a 5mm keyway, and the chunk of cast steel is rather worrying.
It looks like it's for a 20mm diameter shaft, I don't suppose nord pistons take a 20mm gudgeon pin? 
If it's not a small end off a conrod, the only other thing I can think of is a chunk of the center timing gear? The size and profile look roughly correct, does that shaft use a woodruff key though?

The engine seemed to be running fine, I would have though if it was a conrod I would have known about it.
The timing gear would make more sense, when the cam broke it destroyed the head so there would have been all sorts of load on the cam chain - but there haven't been any strange noises or drop in oil pressure so I'm a bit confused...

[festy]

I think I've identified the woodruff key - it's from the broken camshaft, #8 in the diagram below.
So that just leaves one more part to identify...

[festy]

Mystery solved I think, the mystery part is a piece of the large timing chain idler gear, and the woodruff key locks it onto the shaft (or at least it used to) 

[El_4_Romeo]

Interesting. Makes a good case for keeping a cloth under the locating bolts when fiddling with cam timing .

[Al Campbell]

Rather bits in the sump and running O.K. - Had a boss with an Alfetta. Came in one morning and said it was making a noise suspected the big end. Headed down carefully to the workshop about a km away to check it out, was probably a conrod - one piston did a good job at coming out the side of the block before we got there.

[festy]

Interesting. Makes a good case for keeping a cloth under the locating bolts when fiddling with cam timing .

In this case it was nothing like that, I'd swapped over some cams and I don't know whether one of the caps was too tight or something else altogether, but a day or two later I was testing a new alternator when the engine came to an abrupt halt. The exhaust cam had broken, bent a bunch of valves and destroyed the head. That's how the snapped vernier bolt ended up in the sump.
Anyway, the bores and pistons looked fine so I replaced the head, cams and top timing chain and all was good... or so I thought.
Obviously back in 2013 when this happened, the idler sprocket was also damaged and by sheer luck it fused itself onto the shaft and hasn't moved too much since then.

Here's some photos of the damage