I would consider this as a skønvirke brooch made by a Danish, to me unknown maker, C.V.O.L.
The mark "D sledge/ hammer A" is the mark of the The National Association for Danish Enterprise (Landsforeningen Dansk Arbejde). Established in 1908 as a private and independent organisation to support and marketing Danish produced consumer goods in Denmark and abroad.
http://www.cohrsilver.dk/cohr/index.htm
Hope this helps!
Best regards/JAKJO