This frame was part of a large custom built studio console that was installed in Bud Pressner Custom Recordings in Gary, Indiana.  

The frame was removed and shipped to us with little documentation.   Some schematics and diagrams are available.  Each slide in module had a couple of pcbs and all of the circuits appear to be discrete transistor construction that use plg in transformers.  The gray rectangle with the pulls on the front appears to be the module 600Ω output transformer.   There are a number of various modules included in the frame and they break down as follows:

• 16 mic/line preamps
• 2 compressor limiters
• 1 oscillator
• 1 Buffer amp or DA
• 1 card frame

 Price is for the entire package including all documentation.