American Standard has been producing toilets for many decades, and over the course of that time has made a few changes to their part number scheme. Most early lids will have the same part number as the tank, such as 4049, which would be listed on both the back wall of the inside of the tank and the underside of the lid. Sometimes the letter F precedes the lid part number, such as F4049. There are sometimes slight differences in the measurements of F and non-F parts, so it is best to specify the correct part number. Four digit numbers starting with a 2, such as 2092, are used for 1 piece toilets (tank and bowl are 1 solid piece), and numbers starting a 4, such as 4086, are used for 2 piece toilets (tank is a separate piece that sits on top of the bowl).
Eventually American Standard transitioned to a six digit part number for the lid, while keeping the tank number a four digit number. For example, the 735083 lid matches a 4112 tank. During this transition, some lids would continue to get the four digit number, some would get the six digit number. It is possible your lid will have a 4 digit number or a 6 digit number.
