Porcelain was the victorian material of choice for sanitary use and for good reason. It was british made and therefore the quality was always assured, it was tough and sturdy and as you can clearly see, doesn't deteriorate. Sitting in a cold damp building for two decades it still shines like it would've done 70 years ago. The construction of these things is actually pretty damn impressive and must've taken some real expertise. The slab would sit on a revolving, adjustable frame with a cast iron wheel allowing for the slab to be raised and lowered. Compared to many other slabs from similar hospitals this was top of the range. Sort of like a luxury barbers chair but for dead people.