ATM Variable Attenuator Assembly. This unit comprises a Sector Microwave co-ax switch and two attenuators that are preset to change the output level of the C-Band signal.
The co-ax switch manufactured by Sector Microwave is SM7N-B5C2. It has a six pin connector and operates at 28VDC.
We don’t know how it was used, but it could be used in a redundancy package when the backup amp was running hotter than necessary and needed additional attenuation. Even as I write it it does not sound vert plausible – oh well!