It is a Truth single arm entrygard style operator

Thanks for reaching out to us. I'm afraid we don't sell an operator with a 12" arm in this style. The closest we have appears to be the 39-013 and 39-014. However, the arm is 13-1/2" long when measured from the center of the gear to the center of the wheel. Can you confirm you're measuring as shown below?

Dimensions for 39-013

Dimensions for 39-014