If it’s an upper circumstance “L” plus a reduce circumstance “c”, it’s for Louis C Marks who made jewellery within the 40s. Having said that, this interpretation is less likely, as “JP” by itself doesn’t typically signify a certain metallic regular. CN means that the jewelry is produced in China, https://linkalternatifcasper7722109.theideasblog.com/37539536/everything-about-jp88