Truth Entrygard Dual Arm Operator. We would expect you to find 20748 on the linkage arm, which measures 2-7/8" overall length. Other common numbers we would expect to find are 31538, 31539, 30841, 30842, 30472, 30470, and 20748. Also known as a TH-24030 and TH-24031
2-7/8" linkage dimension, off set up.
Order Wi1516 if your link dimension is 3-3/4" stamped 20755.
Order Wi1510 if your link dimension is 4-7/16" stamped 20810.
To determine hand of operator, if your sash lock (window lock), is on the left, you would use a left hand operator. And if your sash lock is on the right, you would order the right hand operator.
Left hand shown.
Part # Hand
WI1515R Right Hand
WI1515L Left Hand
Truth Entrygard Casement Operator