difference between 445577-0125-B1 and 445577-1125-B1

Hello everybody

i'm new on this forum, i need somme help.
I'd like to know what is the difference between 2 models of Brigg and Strattong engines.
The 2 models are : 445577-0125-B1 and 445577-1125-B1.
The parts of these 2 engines seem to be the same.
Someone knows the difference ?

Thanks a lot !