This pin has been waiting patiently for me to find it again, and then to find the pics I took when I got it. I'm ready to share. I think it's Korean, but that's more of a guess than based on any real understanding. I hope someone here can tell me what it says, or commemorates...or anything else at all. Diameter is almost 24mm; the pin-tube is about 8mm long. Thanks!
My wife says that she could make out something about Yokosuka Navy (Japanese) and she says it looks kind of like a pin given for good attendence.
According to my Beautiful Bride, the back refers to the Yokuska First Naval District, which dates the badge to the period 1889 (when the facility established in 1866 in Tokyo Bay was renamed) to 1945 (when the facility became the U.S. Navy's Yokusuka Naval Base at the end of WWII). It remains one of the US Navy's largest off-shore installations, with a small part being used by the Japanese Marine Self Defense Force. The "seal script used on the front is a variant form of characters primarily used modernly for personal seals, which is quite difficult to read. The BB is researching it, and if she is successful, I'll post the translation.
Actually a quite understandable error. Seal script uses many more straight lines and arcs than normal Kanji, as does Korean Hangul, so if you are not very familiar with Asian calligraphy the two can be confused.
One would think I would have become jaded to the abundance of help...and otherwise in-discoverable arcana and detail...available here. But no...quite the contrary: amazement and simple delight continue to keep me freshly thrilled. Thank you all, sincerely.