The customer complained that one of their bathroom toilet lids kept falling down. This is a real problem for men.
I checked to see if the floor was level. I was darn near level but had an ever so slight tilt backward which should have helped the lid to stay up. It appeared to be a defective design.
The only identification is inside the water tank: American Standard 1112 tank, made in Mexico. I suspect that this toilet came with the new home.
American Standard has a pretty awful score at Consumer Affairs web site.
The quick solution was to shim the tank backward a slight bit. I used white heat shrink plastic tubing. The top water tank rests upon a front and rear ridge. I put the shim between the front ridge and the tank and then tightened the tank bolts.
In practice, this solution did work. The customer had to make sure the toilet lid was firmly put up against the tank for it stay in place. I now wished I had used a second plastic tubing shim.
Revised April 7, 2018