So in a bit of a random moment, I stumbled onto some information randomly, though sadly probably still of no great help in eventually cracking this big steel nut. Information is copied below in case the original source goes offline.

https://delta.pastperfectonline.com/webobject/8A69F8A0-E5A5-47AD-BEBD-331731954642

Lockheed Aircraft Service (LAS) EFDARS (Expandable Flight Data Acquisition and Recording System) Digital Flight Data Recorder Model 209. Orange metal case with reflective white stripes. Designed to use 1/4" magnetic tape.

Information from Lockheed Aircraft Service Manufacturer label: 
Manufacturer Numbers: Model Number 209, Part Number 10077A500-103, Serial Number 1223, TSO Number C51A
115 VAC, 400 HZ, 20 WATTS
Weight: 22.5 lbs.

Model 209 was first introduced on commercial aircraft in 1972.