A 15ct gold and platinum-topped safety pin, stamped 15CT PLAT M. This mark was used in the late Victorian to Edwardian period to indicate 15ct gold pieces with platinum fittings, often for added strength or contrast. On this example you can just see a peek of platinum shining through on the top bar.
 
It weighs 1.2 grams and measures 3.8 cm by 0.4 cm. The shape is sharper and more angular than most, giving it a clean, precise look. Closes securely and, like all good safety pins, works beautifully for extending chains or for charm loading. Rare to see in 15ct gold, which was only produced until 1932.