some modern pieces have a moulded 'pontil' depression, rather than a ground and polished feature. If you have a lens take a close look - if it's the latter you should see the faint remains of grinding lines within the depression - they should generally run in one direction only - if moulded then the area will probably appear very shiny and very smooth. W/Fs produced textured pieces in lilac and aubergine, so some confusion re the colour is understandable, but the base and shape are unrelated.