Do I have a Open diff or lsd??

I have a 1993 Mazda Miata , 5 speed Manuel, all this time I’ve thought I have a open diff, but this information is from the dealership, did some miaras come with a Lsd that were not 1.8

I have a 1993 Mazda Miata , 5 speed Manuel, all this time I’ve thought I have a open diff, but this information is from the dealership, did some miaras come with a Lsd that were not 1.8