I have heard of platinum being rhodium plated before on rare occasions, but I would assume it is not. But there's not a thing wrong with asking! White gold is plated because it is yellowish. Platinum is already white (silver, actually), so there is no need to plate.
If you want it to shine then you rhodium plate it. However since platinum is softer than gold it's prone to scratching and the plating will rub off quickly.
If you want it to shine then you rhodium plate it. However since platinum is softer than gold it's prone to scratching and the plating will rub off quickly.
Matter of taste, really - I much prefer platinum because I like the heft of it, I like the way it displaces from a scratch so that it can be polished back to its original condition, and I like how the ductility makes for safer prongs.
Concerning rhodium: it's basically a cheap and non-labor intensive way to make metal look shinier. The plating won't rub off more quickly, but it's a micron thick, so as the metal underneath it wears, so, too, does it - which means the shine won't last forever. Honestly, I'd just ask the jeweler: I prefer mine unplated, too, because I like the look of greyish look of platinum more than the whiteness of rhodium.