This matches a pair of earrings also for sale. See the last photo for the set.The necklace is 18" long and 1 7/8" wide. It weighs about 100 g.
The locking piece will come out if you pull it apart hard. I think the folded wedge piece needs to be opened more but I didn't want to mess with it. I think a screwdriver forced it will open it enough that it will be super tight.
The little bump piece that sticks up for you to push on came off years ago so you have to go in between the opening to push on the clasp to loosen it (see photos). This stamped Mexico, 925 and T5-79 (to the best of my eyes). This item is in the category "Jewelry & Watches\Vintage & Antique Jewelry\Necklaces & Pendants".The seller is "dogloverjb" and is located in this country: US. This item can be shipped to United States.