help! strange Atari box

I went to a surplus store last week and found an odd Atari box. It says it's an Automatic ROM/RAM Tester. It has two rows of address switches, one switches on one row are labeled 10 through 0 and have LEDs above them. The second row of switches only has five switches and they marked 11 through 15 and don't have corrosponding LEDS. Switch 11 is directly below switch 10, switch 12 is below switch 9, and so on. It looks like they may be multiplexed somehow. The box also has 8 Data switches and LEDs. The are four low insertion force sockets on the box, two are for 25 pin DIPs and 2 are for 20 pin DIPs. There are also various other switchs marked 1K/2K, RUN/STOP, Read/R/W*, and GAME/BOX. There is only one connector on the box, it goes to a 50 pin card edge connector via a ribbon cable. There are no power connectors or other connectors on it so it has to part of a larger unit. Any ideas? Anyone?