Hi C.B.! 

First, Thank you for your interest in PurePearls.com! To answer your question: I hardly ever recommend purchasing any type of jewelry as an investment (with the exception of very rare colored gemstones such as Brazilian Paraiba Tourmaline, Russian or Brazilian Alexandrites, Kashmiri and Burmese Sapphires of very certain colors, Burmese Rubies and certain Emeralds). Cultured pearls- like all jewelry- are meant to be worn, enjoyed, and possibly passed down generations. This is not to say that your cultured pearls will not be worth what was paid for them, but rather they will not appreciate in value as would a rare vintage or a work of art… Cultured pearls are a manufactured, farmed gem; control of international supply and demand are carefully monitored so that each year harvests do not flood the market and devalue existing stocks, nor that certain items become so rare that their value skyrockets.
 
The only exception to this -ever- is with Natural and Exotic pearls, in which case you would need to start searching auction houses and fine estate jewelers. Additionally, there are the early Mikimoto productions that could be valuable circa 1912-1930(ish), however, unless the pearls are accompanied by the original clasp with the famous ‘M’ Hallmark, box, appraisal papers and invoice, then the pearls would likely be valued at current cultured pearl market values as they would have no provenance. Lastly, it should be noted that neither Mikimoto’s nor Tiffany’s culture their own pearls- their pearls are purchased at the exact same auctions and production centers that everyone else imports their pearls from; indeed, Mikimoto Pearl Company stopped culturing their own pearls in the early 1960’s to focus solely on their retail operations worldwide.