Is it hard like ceramic or relatively soft? Could be Lincrusta or similar.

In addition to how hard it is, what are the thermal properties? Ceramic tile tends to feel cooler to the touch than something like Lincrusta (that is, heat transfers more readily from your hand to tile, glass or metal than it does to wood, paper, or linoleum). If it's tile, you should be able to feel the difference between the tile and the grout. If they are individual tiles (the squares and hearts), the gaps are such that a sanded grout should have been used and you should really be able to feel the texture change. Though it looks like everything may have been painted, which will make it harder to figure out what's what.

It’s definitely hard (I wouldn’t be able to scrape or chip it with my nail) and I’d say it stays cooler. There are no grout lines and that’s what’s so weird & made me think it was stamped. It looks like the stamp or tile is the clover shape with one square in each corner. I’ve searched the internet and can’t find a similar example!

When there are four leaves I think it’s called a shamrock. Honestly, I thought it was four hearts.

With the repeated pattern and marked irregularities in installation, it does resemble tile a bit. Actually it looks like a decorative garden tile that has been painted. Painting over grout makes the grout disappear, but any of those depressions could have carried grout. While it could be a stamped tin tile, they rarely come with such a deep relief.

It doesn’t matter what the material is, it matters whether you like it and want to keep it, or would like to remove it. Should you choose to remove it your mystery will be solved.

Thanks. I think I was also curious if there was any sort of history to it, you know? Doesn’t seem like it but I had just always wondered if it was fitting for the era of the house.

Yeah, @cupofkindnessgw, of course it’s a four leaf clover. I’m Greek. I should just stick to what I know: medicinal herbs and vase painting. And tile.

I wonder if it is stamped plaster?

I think it is tile that was painted over.

Another vote for tile that was painted over - can you try to scrape in an inconspicuous spot?