The porcelain condensor or transformer bushing appears to have been cast in a two part mold, it has a very thin mold line along the vertical axis.

The brown unipart is a mystery to me, I've had it for several years, and I've never seen another one like it. What is its U-number (if it has one) ? Its height is about 4 inches, and the wide part of the skirt is 3 inches.

Neither insulator has any visible incusing or markings.

Rick Soller informs me that this is most likely a U-584, and that it falls within the range of U-582 through U-588

Here is a [id=252329286;U-583] and a pair of [id=263430711;U-588] to compare with it