This module was advertised as "concert hall" acoustics with maximum flexibility. It consists of two units, the control head electronics and the reverb spring assembly. This kit was $25.95 in the 1976 catalog.
PAiA 4712 Reverb Module User Manual
PAiA 4712 Reverb Module Schematic
The reverb tank is an Accutronics 1FB2B1D.
The Accutronics model 1FB2B1D specifies:
|1||Type 1 case 9.25" x 3.375" x 1.313"|
|F||Input impedance 1475 ohms|
|B||Output impedance 2250 ohms|
|2||Medium delay 1.75 - 3.0 seconds|
|B||Input grounded, output floating|
|D||Vertical mounting with connectors down|
The original module had RCA cables soldered to the PCB but I changed them to PCB mounted female RCA connectors so a longer cables could be used for mounting the reverb tank. One of the RCA jacks crowds C3 but I used a bipolar capacitor for C4 so omitted C3 anyways.