Filled my cooling system tonight, where is the "cold fill line" in Moroso tank?

[shark92651]

Tonight I filled my cooling system. I poured just short of 4 gallons of the Ford orange coolant/distilled water mix at 50/50. It went in no issue and could hear it bubbling and filling the system. I stopped about 1 qt short of 4 gallons and the Moroso tank looks to be about 1/2 full at this point. I figured I would stop there and after first start, and then after cooling, I will check the level in the tank and top it off. But where is the "cold fill line" in this tank. There is no sight glass or anything that I can see would indicate a level. What do you think?