glupson
This can be used to advantage today, especially on a turntable with a threaded reflex clamp. If the LP extends beyond the platter, the LP can be made to be flat against the platter. If the platter and LP were the same width, the LP would be "dished" if you tried to clamp it to the platter.
LP on one of the pictures seems to be bigger than the platter. Wouldn't that have some potential effect on vibration, or something else?Not necessarily - some turntables are designed that way. If you look at the profile of an LP, you'll see the center label area and the outer edge are thicker than the rest of the LP itself. That's a throwback to the days of automatic record changers and stacked LPs. (With the raised center and edge, the grooves of a dropping LP theoretically wouldn't contact the LP below.)
This can be used to advantage today, especially on a turntable with a threaded reflex clamp. If the LP extends beyond the platter, the LP can be made to be flat against the platter. If the platter and LP were the same width, the LP would be "dished" if you tried to clamp it to the platter.