Vintage Covered Butter Dish, Glass Tray

I’ve had this butter dish for many years and have no recollection of how I came to own it. I used to go antiquing frequently so that’s most likely how I came to have it. I hesitated to clean it prior to posting because I’ve read both positive and negative thoughts about this. On the bottom I’m able to see a triangular symbol (see photo of page from online catalog) with the words copper and silver. It seems likely that it is a silver plate on copper item by Ashworth. I hope this helps! Approximate Dimensions: 7” X 4” Weight 14 Ounces