There does not seem to be an expert that is familiar with the marks. This is why this has not been picked up. I have been out with back surgery, just on a short time starting today, I happen to see how long this was on the board, thought I might make a suggestion to you. I would take this to a jewelry store that sells estate jewelry, they will have many books on older pieces where they possibly can look this mark up to tell you who made it. You can find them in the phone book or by google, just make sure to look for Estate Jewelry.
An Estate Jeweler would have the information on the silver also. They keep a lot of price guides and informational books. I did a quick search in my books for YTK nothing shows up.