I've found a handful of these strange things in a stock of new old stock components, in the middle of capacitors, resistors, old potentiometer knobs and such lovely surplus cheap stuff.
They measure 1" x 0.5" each and they seems to be mainly made of white ceramic. I've found only these variants (green with two pads and blue with three). The surface of the pads is conductive.
The other side is white ceramic with no visible features. It seems that the entire content is 'printed' on this side only. No ID or other information are printed, or engraved, or whatever.
The visible snakey "path" between the pads (protected by the colored paint) suggests that some sort of current should flow between them, but the DC resistance between the pads seems to infinite (or at least > 2MOhm), even between the closest pads in the blue one. I've even tried to apply 12V DC tension with both polarity, but no current flows.
The shape of the 'circuit' in it suggests some form of inductance (HF antenna?), and the blue one seems to be a variant with a tap closer to the top pad (like a transformer). But shouldn't inductors be still conductive at DC level? The same if they should be fuses or other current/voltage protection device.
I haven't tested capacitance but I don't expect them to be capacitors... or not?
Random googling hadn't helped much. I've never seen something like this before and I'm really puzzled now!