The other snapped crankshaft that Thob alluded to appears to have resulted from a poorly finished GM90 (internally balanced) crank pin with no fillet machined on each side of the pin. However that one happened after 20,000 hours pumping water, so I think Noel got his money's worth out of the engine.
From the last picture it appears that your break started at the same place as did Noel's, but a fillet is clearly visible in the photos, though it's not machined particularly well. Perhaps just a bad location to have a void in the original casting? These are 3rd World engines, after all, built on 1930s technology. Stuff happens, as we all know. The fact that it doesn't happen more frequently is remarkable.
Gary's offer is extremely generous. Above and beyond what anyone would expect. Kudos to you, Sir!
Quinn
[Edit: Looking again at your last picture, it looks to me like the rough casting was machined right up to the throw web. The break might have started on the outside of the web and propagated across it and finished at the pin. Same reason for failure as in Noel's GM90 engine (stress concentrating at a sharp corner and fatiguing the metal), but starting on the opposite side of the web.]
