A Planter Plate,... but 'Not'

I'd been asked by my elderly Aunt to re pot her African Violet for her; (over 25 yo plant). I learned the hard way that the pot sits in a deeper dish because it's watered from the bottom. While cleaning both pots I came across this little plate being used to lift the plant off the bottom. Covered with scale from all the watering. When i got it clean I was shocked of how pretty it is.

No there isn't any mark on the back what so ever. I thought 'ashtray' too; My Honey said it looked something like a resting plate for the relish fork, or for the coffee or tea stir spoon at ritzy type functions back in the old days.