Antique 900 Silver Card Holder / Calling Card Case

Circa late 1800s. I am not certain on the Silver content. As you can see when I scratch, tested with acid, it gives the same blue color as sterling silver, but it’s slightly spotty, which is what leads me to believe that it has a high silver content and is probably 900. 90%. This is a really cool case. I believe it was used to hold calling cards. Possibly cigarettes but leaning more towards cards. Which was a piece of paper that had a man’s name and address and usually a special message. these cards would be left at someone’s home like an announcement. A lot of times single men trying to court women. Think of Bridgerton. It has initials engraved on the front CTM. Beautiful engraved design on the front and the back. The top lifts open. There are two circles on each side where you could attach a string. It’s about 3.5” by 2.25” I do not see any markings on it. Really cool piece. It’s just under 70 grams. See pictures for best description. There is a tiny dent in one of the bottom corners