No you clip it on your belt to hang a purse or chatelaine. Google silver chatelaine hook for more examples. At the moment i am travelling, no access to my library. Will confirm maker's mark after 23rd of April.
Yes, the hook is puzzling in regard of chatelaine. I recall a forum member from Denmark (I think) asked about the function of similar item and then explained it was for embroidery girls worked on and kept them on hook attached to the belt whenever they needed to go around. Regards
Checked the maker's mark of; Johan D.(Diederik) Jansen in rectangle ; IDI with serif . Johan D. Jansen known maker of dinner sets, tobacco jars, kettles and sauce boats. The belt hook maker's mark unknown /perhaps possibly made by Johan. D. Jansen. In Dutch the hook is called zilveren wol haak/naaihaak or kluwenhouder or Yarn holder / thread holder Some other examples: