From trying on. They would have been worse than that the first time you wore them anyway. The discoloration will brush right out, it's just how shell is.
The description doesn't say whose coat it was or date it, but Lucius Beebe was a regular at Poole, and from The New Yorker, 1937:
He has a good evening dress coat lined with mink and collared in astrakhan, which he has insured for $3,000, and an old rag also lined in mink, but with a sable collar, which didn’t seem worth the bother. The jewels necessary to set off this splendor, or else hold it together, include three gold cigarette cases (although he rarely smokes anything but cigars), valued at $700 each [in 1937 dollars], a cashmere sapphire cabochon ring worth $1,200, a single emerald stud at $500, and a platinum evening watch which cost $10,000.