Join Date: Oct 2015
Model: GL1500SE Euro Spec
According to partzilla parts catalog, left and right disks have different part numbers such as
45251-MT8-000 DISK, R. FR. BRAKE
45351-MT8-000 DISK, L. FR. BRAKE.
And they are only interchangeable between 1990-2000 models. You may want to check the model year of the part.
Since they have different part numbers there may be some differences, I don't know.