I purchased an upgrade which gave me a base quoin limit of 110 per day. When I hit 100 I sailed on past, and when I hit #110, the pop-up over my head said "You have reached 100 quoins today!" (which I'd done a while ago: it probably should read "max" instead of "100").
Then I drank a Potion of Avarice, and it increased my max to 150 (as it always used to). I'd like to suggest that it OUGHT to increase one's max by +50, rather than to 150 total (since there may be other upgrade cards available).