[gafftaper]

True DMX standard should have 5 pins and only 5 pins. Two of those pins usually aren't used. Sometimes manufacturers cut it down to three pins. Sometimes power is added and you have four pin scroller cables. But that's just messing around with what is convenient for their products. Seven Pin? My guess is that it's some sort of pre-dmx proprietary control cable or an analog cable as pointed out already. There was some time between analog control and when the DMX standard was adopted were every manufacturer had it's own sort of digital control. Another possibility is some sort of modern adaptation to make the old technology work with current cable?

If you find an old Cinch Jones cable you'll see about 20 pins. They have a rectangular plug. Remember in the "bad old days" before DMX you needed a separate wire for every dimmer you were controlling.