Hi, I'm trying to bring my wife's old bike back to life. It's an argentinian made mixed frame, with sachs-huret derailleurs and a three speed freewheel.

I'm stumped at the freewheel, as I need to remove it in order to overhaul the rear hub. I'm no bike mechanic, and I have never seen one of those. Can you help identify it, and which removal tool should I use?

Googling the text ('Unity gears') only brings me to ebay auctions.