Ok, It looks like the guesses have subsided for a bit, so here goes.
When we moved in, it was used as a filter for the pool. The water entered the bottom manifold and was pushed up through the three tubes. Inside of those tubes are a "mesh" sleeve with wire spring support. On the sleeves you slid a "felt/cotton filter sock. The water went through the filter sock then the sleeve, back out of the top to that manifold and back to the pool. Made the water crystal clear, but startup in the spring was terrible. Every 1-2 hours the filter sock had to be changed. Each manifold had a butteryfly valve along with a valve for each tube, top and bottom. ALL stainless steel except the valve bodies, the are brass.
What was it originally......??
Part of the beer/water filtering system at Anheuser-Busch. The previous owner worked there and salvaged the pieces/parts to put this together. I assume the filter tubes were much longer in the plant, the filter socks are 10' long and have to be cut off to use.
This thing must weigh 300-400 lbs. I was trimming around it the other day and the RFM wheel caught in one of the supports and before I knew it, it was on top of the mower and one of the handles caught the tractor. Actually in one of the photos, you can see red paint on the leftmost tube. Guess what color my mower is???