This is a very nic original fuel mixer or carburetor for a 6hp or 3hp Fairbanks Morse Z throttle governed gas engine.  It has a dog leg in the throttle linkage which is for a 6hp engine but you could easily swap it out with a stright one for a 3hp engine.  It is part number ZCA4A and mounts with two holes 3 1/4" apart on center.  The throttle hole is 1 1/4" in diameter.  It is in very nice condition with no cracks, breaks, or repairs that I can see or know of.  Both fuel needles move as they should.  The throttle shaft and plate seem to have VERY little wear.  The compensating valve is in great shape and this carburetor should be ready to go to work for you.  If you've been looking for one to complete a restoration because yours is missing, broken, or repaired here is a very nice one.  The pictures tell the story.  I can always be reached by phone or text message at 262 573 193 1 if you'd like to talk about it.  Good Luck.