The 576 is semihollow, laminate top and back with solid rims. Here's the spec from the '89 catalog. I have the H525 which is thinner, laminate like the 576 but fully hollow and with P90s. It's a bit like a smaller version of the 550 to my thinking. 16" vs 17", 24.75 vs 25.5 scale, both semihollow, so you should have a center block. 2 3/4" thick vs 2 7/8"
It's not shown in the 2005 catalog that I have. It was shown in the '93 catalog.