Many thanks for providing translations from Thai for some queries, even old ones, it is much appreciated.
Glad to hear that the Korean marks page is proving useful.
Those are excellent photos of your Korean items. Please post each question / item separately, in order to avoid confusion later on. I'll be happy to answer your questions, one by one.
Here is the answer to your first question:
The two characters 貞信 mean "constancy / chastity" and "faithfulness." Looks like the perfect gift to form part of a bride's dowry, but might possibly be a company's name and logo. Definitely post-Korean War, my guess is that they date to the 1970s or 1980s.
Look forward to your other posts.