Help identify add-on board inside Tek 547 scope.

[Martin Hodge]

Does anyone recognize this Tek 547 add-on board? It connects directly to the deflection plate pins of the CRT and has a 4pin xlr connector accessible through the left cowling. The board has 2 sections labeled "vertical" and "horizontal". It gets +/- 12.6 volts from 2 pins of the xlr connector and appears to provide shielded, single-ended H&V signals to the other two pins. Google Tek wiki have come up nill.