Looks like a standard telco demarcation hut but I disagree with the speculation that it's likely related to DOD circuits for Offutt AFB. AT&T provided just about all of the telco services for the US gov't back in the Cold War so many of the demarcations between AT&T vs DOD ownership was right at the actual frame room(s) on the base. In the case of HQ/SAC at Offutt, AT&T had a semi-hardened facility (I hesitate to call it a 'bunker" because that word has certain connotations) tucked-away in a residential subdivision just off the installation, near the old SAC Museum. SAC & most other DOD circuits -- AUTOVON, SACCS, SACDIN, AUTODIN, etc. tended to require some protection that a standard telco hut didn't provide.
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