Westminster Clock

This is the reason why your strike spring has broken. The original detent has gone,probably ran of when the man with the hammer and nail came along.

Any way who ever attacked this with the hammer decided that he hadn't done enough damage, so got a file and filed the snail down. If you click on the picture below you can see.

The nail does not work. Removed it and put the detent back where it was supposed to be. I have put a new snail on and it is doing what it supposed to now.