Lori,
The number 31538 is found on at least 5 different Truth Entrygard Operators, here is link to the list: https://www.homewindowrepair.com/catalogsearch/result/?cat=&q=31538 . That being said, this page might be the most help: https://www.homewindowrepair.com/truth-entrygard-dual-arm-operator-information.html
Greg.
Dave,
The numbers that really help us the numbers that start with the number 2, so something like 20810, 20755, 20748 or 20544.
Greg
Thanks
Dave
My guess would be the right hand, Wi1510, shown here: https://www.homewindowrepair.com/truth-entrygard-operator-20810.html
Greg
patent US 4.241.541
patent CAN 350.432
patent 1982
Robert,
The only way to know for sure is to see a picture of your operator. But from what I am reading, I would say you have the Wi1510, The Truth Entrygard Operator 20810,shown here: Truth Entrygard Operator 20810
Greg