Peter, failed coils are not all that common on these bad boys, although even if we had the "thing" that tests the coil, yours would probably show up as ok, until it got hot. So in my opinion, and in the absence of a coil tester, the best check is to hot run it. if you can work the mower for 20-30 mins and the coil doesn't fail then it probably wont fail at all. They normally fail within the first 10-15 mins of running when they're dodgy.
Looks like you've got another one there ready for a new home.
