I'd suggest the fact it rests on two outside curved supports only would likely discount the insulator theory - from memory all the insulators I've had are supported on the entire base area though again, from memory, some of those do have lemon squeezer undersides. There appears to be a lack of abrasion on the inside of the cavity, so again I'm thinking no piano foot has ever set foot inside this one, and the cavity has perhaps less depth than your average insulator. But he ho, give me another three - and a baby grand - and we'll see if the suggestion works. The fact it wobbles a tad is irritating - I've half a mind to rub the thing on some w. & d. and level it up.
It's a very unusual shape - neither round nor square - and the circular supports I'm sure give a nod to something classical.
both the top and sides have been ground and polished - under a loupe the lines can still be seen - also the narrow top ledge at each end, though the remainder is as it came from a mould I believe.
Can't show you by means of a photo, but when viewed from the side the original pressure/swirl marks - where the gob was forced into the mould - show up as a web of faint lines and curves in the main body - quite attractive.