Thanks for the extra photo, that helps a lot.
Your teaspoon is an example of the typical bamboo-handled flatware made in Bangkok, Thailand in the 1960s and 1970s and brought home by the tens of thousands by Vietnam vets at the time.
It's probably nickel-brass (or possibly gold plated nickel-brass) which is common in Thai flatware, but it's not sterling or solid silver or solid gold. Your local jeweler would test it for you in about two minutes, but I think you'll find it's nickel-brass.
The mark is a flatware manufacturer's mark, not a hallmark, but which maker it refers to it's going to be almost impossible to say as there's no known published register of late twentieth century Thai flatware manufacturers.
It doesn't have much value, I'm afraid, just a $3 to $5 at the most if you saw it for sale in an antique store as there were and still are so many of these bamboo handled sets being produced, not only in Thailand but also in China, Korea and Japan with brands such as "Supreme Cutlery", "Stanley Roberts" and "Oxford Hall" to name but some.
I do hope this helps!