What the heck is this for?

[senormechanico]

What is the purpose of this black box I found and why was it installed? The insides are obviously Raymarine brand even though there are no names or other identifying things on the outside.

I ran across it while cleaning up a poor wiring installation done by the previous owner of my boat. All my instruments are Raymarine with the exception of the GPS/chartplotter which I'm replacing with a Garmin 5208.
(Whooeee is it a nice unit!)

This mysterious box was hooked up such that it constantly drew battery power, but as far as I can tell it wasn't doing anything. There are 3 wire bundles coming out of it. One is a 3 terminal Seatalk wire, and the other two have been cut off about 6 inches out of the box and redone with after market wire. One of those is hand labeled DATA and another is hand labeled POWER.

I traced the Power lead which had been connected to the house battery, and the Data leads went to the autopilot and also to the GPS NMEA terminals.

The inside of the box contains a Raymarine circuit board with several computer microprocessor chips, a crystal labeled 12.0 for the processor clock, a 5 volt regulator and a few other integrated circuits as well.
One of the microprocessors has a V 05 label on it and a sticker on another chip says
NAUTECH
A090694

Another chip is labeled
NAVDATA
09731

The circuit board itself has a number etched on it.
3015-053 A NAVDATA

I suspect it is either a Seatalk to NMEA 0183 converter or NMEA 0183 to Seatalk, but I'm not sure. All my Raymarine instruments work normally without this box.

As I am in the process of installing a chartplotter which needs NMEA 1083 or NMEA 2000, it would be great if I could read the Seatalk information on the plotter.

Thanks for your help!

Steve B.