"New" to me 135 Gallon

I just picked up an older 135 gallon tank that is some kind of heavy. I'm quite puzzled by it and the stand/filtration. The tank itself has three holes drilled in the bottom; two along the rear of the tank about a foot from each end and one in the front left about the same distance from the end. These holes match the placement of the legs on the stand which have PVC ran inside for overflows/returns. Inside the stand is a filtration system that contains a UV filter, a pressurized canister, along with a little giant return pump which feed under the floor and up through the PVC. I will attach pictures shortly to see if anyone has ever seen such and can offer advice as to what this contraption might have been used for along with any input on how to setup for mised reef use.