It wasn't until I was photographing this that I noticed a maker's mark on one short end (the end with the pour hole), for T Mills & Bros, Phila. Founded in thee 1850s-60s, Thos. Mills & Brother was a leading manufacturer of candy molds and other confectioners, bakers' and ice cream machinery and equipment. I believe this is a candy mold (maybe for a sucker, which could be hung from a string around one's neck!) and a fairly early and scarce one (I can find no match of it), I believe made of lead. I of course love anything with a clock face, and this one a bit imperfectly spaced in a very good one, reading 1:30, or 6:05, I'm not sure which!  

Each side 2 3/8" x 1 5/8".  Very good antique condition.