American Rose plate

I had found this plate after it had been in storage for years after my husband's parents passed. They got the plate from my father in law's mother who lived in South Dakota. I believe this is where the plate was purchased. I'm sure this was a high dollar item back then as times were very hard. I would just like to get as much information on it as possible and see what it would appraise for if we ever did want to sell it. One other thing I'm curious about is the L-52 numbering on the back of the plate.