Both in Hib and Fang Cove I ran into this

> exch 1301 plat kron for doko
One of the guards barks out, "No, sir. I'm afraid you'll have to work with values no greater than 100 platinum at a time."

But I was able to do this

Wealth:
924 platinum, 1 gold, 15 silver, 24 bronze, and 16 copper Kronars (9242756 copper Kronars).
No Lirums.
209 platinum, 9 gold, 8 silver, 5 bronze, and 6 copper Dokoras (2099856 copper Dokoras).

> exch all kron for doko
You count out all of your Kronars and drop them in the proper jar. After figuring a trivial fee in the ledger beside the jar, you reach into the one filled with Dokoras and withdraw 646 platinum, 9 gold, 4 silver, 8 bronze, and 6 copper Dokoras.

I think that the guard means to say 1000 platinum at a time, not 100.