I'll assume that you have an F series engine on your Lawnboy. If so, there are quite a few different part numbers that cover the same coils. The main difference is if you have a newer "zone start" or older model with the ignition switch mounted on the cowl.

The difference between these two ignition switches is that one has to be connected to ground to run and the other has to be disconnected from ground to run. The "open to run" coil will work in either style mower, it's just that the ignition switch on the older style will be backwards (off will be on and on will kill the engine). You can't get a zone start to work properly with the "ground to run" coil.

If your mower is running with the new coil, you are in good shape.

Thanks for your response. In fact the mower has a zone start, F-series engine. I had two spare coils which are both from zone start, F-series mowers and except that one is black and the other is grey and they have different numbers, they otherwise appear identical. The mowers with the ignition switch on the cowl must be pre-1990 or even older.