Received these as a gift a few years ago and use them about once a year to look at stars in the desert.

How do I tell what tubes are in them?

AN/AVS-6(V)3, ANVIS
NSN 5855-01-475-7061 US

https://www.dropbox.com/s/io0974ij0sdguct/3rdGen.png?dl=0

Why, it's an AN/AVS-6(v)3, of course.  

They're usually referred to generically as "ANVIS," Aviator's Night Vision Imaging System.  The specific nomenclature is a Joint designation, standing for:

"Army-Navy / Piloted Aircraft (A), Visual (V), Detecting/Ranging and Bearing/Search (S) - 6th Model, Version 3."  

The (v)3 is the latest generation of the AN/AVS-6, which is most typically associated with Army rotary wing (helicopters), while the AN/AVS-9 is more commonly used by the Air Force in fixed wing aircraft, however, yours also has the older objective lens design, not the newer, "lobed" objectives.  

While ANVIS were originally designed for, and are typically associated with aviation applications:




They became quite popular with ground-based Special Operations Forces (SOF) due to their superior image quality and optics, and improved depth perception before more "hardened" binocular night vision devices (BNVDs) such as the AN/PVS-15, intended for use by ground combat forces, became available:






Yours also comes equipped with a COPS, or Clip On Power Supply, to allow the device to be used for hand-held observation, rather than helmet mounted.  

In general, ANVIS are considered less durable than most ground-hardened NVDs, as they were designed to be used with aircraft cockpits, and are far less water proof/resistant - however, some still like them because of their excellent optical quality, light weight relative to other BNVDs, and relatively low-profile when stowed.  However, for helmet mounting, they require specialized mounts and remote power supplies that are not compatible with most other NVDs.  




Jeeze, I wish I got gifts like that.  

~Augee

thats one hell of a gift

Thanks guys, great info.