Jas3924, don't know what area you are in. What is the size of it? That will help determine value.
The cost appreciated is dependent upon the demand. If you are in a trendy area it will go higher. If you are in a small town or country area...it will go lower or not at all. If it was Coca Cola, A&W Root Beer or a nationally famous name it would go for more. But depending where you are, Merita is a recognized name in the SE.
My best recommendation if that you search "vintage diner soda fountain menu sign" and "antique menu sign" to see what they are selling for. Many people are listing them on Ebay for $200 up...but they aren't selling. So, unless you need to sell it fast, look around and see what the market is. There are a few that have offers on Ebay...Sellers are listing them for a price with best offer! Monitor those if this is the route you are going to take.