Pretty sure you meant to say "Black Diamond" grade. Black Beauty is a Baker gun.
Some of the Shapleigh hardware Tobin guns were called "Blue Diamond" guns, and had blued frames. I don't know how much difference there was between the blue finish and the black "Pyro oxidized" Tobin finish.
My 16 is case colored, and marked "Tournament". Someday, we might know who the Tournament guns were built for.
$250 is a parts gun price, and a cheap repair can be had at Mike Orlen's shop, but, I wouldn't put too much money into it. I'd also look for a different gun that wasn't loose.
Best,
Ted
