The Blue White Industries Flexflo Peristaltic Metering Pumps are chemical feed pumps designed for accurate and hassle free delivery of liquid chlorine and acid to pools, spas, hot tubs. and smaller aquatic features (aquariums, recirculating fountains, etc.)
This is NOS (new old stock) bought for chlorinating a well water storage tank but never installed or used.
Sells on Amazon for $680 (with free shipping) but some online pool supply outfits offer them for around $550.
Used ones on eBay go for $175 in “unknown working condition.” (?????)