Yes, the disc closes off the low pressure side so you can remove empty cylinder for filling.Doesn't really look like a tee, but I guess it is. What controls the rubber disc that switches between the two sides ? Does it allow refilling one tank without turning eveything off ?
So I'd either snatch the first-state regulator from the propane company's tank when they remove it (but it's really old), or buy a new one, and plug this into it. Then connect my two 40lb tanks to it.