Giving it a second thought, I believe it is indeed a planter. I guess the top was designed to hold 4 square flower pots (probably included but now missing).
Would be very interrested to see a vintage ad / catalog if someone has one...
I see it with four round pots of different heights, depending on plants and situation. The "X"-shaped ribs were probably molded in to add rigidity. I could also imagine it as a great play table to contain bits like Legos or other small children's toys.
I have the confess, the reason I kept the coffee table, aside from it being a large square and very low which looks handsome, was the fantastic hardware on them. Those brass(?) screws and fittings are so nice. I'm weird.
