Leaking Toto Drake

I just purchased a Toto Drake toilet and had a plumber come seat it for me. I was disappointed to find a small leak coming from where the tank bolts to the bowl on the left side under the handle. The plumber came back out and reset the tank but it is still leaking this morning. Will it eventually seal itself or should we do something different? Help!
Wackysue

The casting may be a little rough. The general recommendation is to take some sandpaper and sand the inside of the tank where the rubber washer fits prior to inserting the bolt and washers so it is smooth (only takes a few swipes usually). If the metal and rubber washers are installed properly, and that area is smoothed, it should be leak free. The two bolts should be tightened equally as well so the tank sits symetrically on the base.

We like to sand the inside of the tank first.

Instructions below.
https://terrylove.com/forums/showthread.php?t=743

Any grit in particular that you'd recommend?

We use emory cloth, but most any sandpaper will do.

Emory cloth is the best by far. You can get a small box of it in any plumbing supply shop. It's handy stuff to have around.