Here are seven close relatives to piano insulators as follows - all for $25 plus actual postage!

Two "Jelly" style candle holders -- these were undoubtedly made from reworked piano insulator molds as the dimensions are identical!

Casters as follows -- front left to right:

small clear with no markings

Great amber marked A under an H (Anchor Hawking)

larger clear marked A under an H (Anchor Hawking)

Beautiful yellow with no marking -- light wear on base

(upper right) dark amber marked A under an H (Anchor Hawking)