Truth Casement Window Operators

Hello there. This looks a lot like the 39-253LB and 39-253RB Dual-Arm Operators. Review the dimensions below to confirm this matches what you have. This operator pair is also distinguished by having the square-shaped 39-529 Track Slide, sold separately, at the end of the straight arm. Judging from your photos I am fairly certain that's what you have, but do double check to be safe. Let me know if the track slide is a different shape, such as more rectangular. For new covers and handles, see either the 39-375 and 39-376, or the 39-451 and 39-452. Both sets work with these operators, it just depends on the style you prefer. 

Dimensions for 39-253LB

The difference is the guide at the end of the arm. As mentioned above, the 39-253LB and 39-253RB use the 39-529 guide (sold separately). The 39-438B and 39-439B, however, have their own guide built into the end of the arm. It's a different design compared to the 39-529 and therefore not compatible. 

The video below will explain exactly what I mean.