Interesting Silver Wing. Maybe the previous owner spent time on here and imported what are probably Fehling pannier rails to fit those Givi 46 litre panniers/saddlebags/side cases on. It's an added bonus for anyone over the Pond wanting a Silver Wing to do a bit of touring with the lady wife.
I'm not a fan of hard panniers these days, they're fine for carry stuff securely but unless you have some type of inner bags, using them as suitcases can be impractical as the backs can get covered in dirt and road crap. Which can cause problems if you check into a nice hotel plonk them on top of your nice clean bed to unpack.
I had the same sized Givi pannier as a top on a used 2002 Yamaha YP Majesty 250 I bought years ago. I found it impractical for my needs as it took a full face helmet and not much else.
One thing I noticed when I fitted Givi soft throw over bags when Mrs M used to tour with me, they have to sit higher on the flanks of the Silver Wing away from the exhaust heat and don't get covered in crud.
That design of Givi pannier also reminds me of the early Burgman 250 from the Nineties The German importers used to offer a rear rack tomount a single pannier/saddle bag/ side case in the vertical position, it looked as weird as it sounds explaining it.