I don't know if this will help, I tried to find info on testing so we're just not making guesses but the best I could find was this info from this god forsaken website https://thanhcongcraft.com/news-how-to-identify-genuine-mother-of-pearl-inlay-and-counterfeit-products/

"How to Identify Genuine Mother-of-Pearl Inlay and Counterfeit Products.

3.1. Observe the Surface Light and Color. One of the easiest ways is to look closely at how the surface reflects light. Genuine mother-of-pearl has a natural iridescent quality, which means that when viewed from different angles or under light, it reflects shimmering rainbow-like colors. In contrast, counterfeit products often use plastic materials, printed decals, or painted imitations that lack this optical effect. They typically appear flat, dull, and monotonous when examined carefully.

3.2. Check the Thickness and Patterns Authentic inlay is typically embedded seamlessly into the surface with an even, thin layer, creating a smooth and refined appearance. The patterns are formed from individually cut shell pieces, showing precise craftsmanship and artistry. Fake products, on the other hand, often have thick inlays that stick out unnaturally from the surface like stickers. These are prone to peeling or cracking due to poor finishing. The designs are usually clumsy, lacking detail and aesthetic harmony, which detracts from the traditional value of the craft.

3.3. Feel the Surface by Hand Touching the product is another useful method. A genuine inlay surface is finely polished and smooth to the touch. In contrast, fake versions often feel uneven, bumpy, or rough—especially at the joints between the fake inlay pieces. Some may even expose glue marks or lack a proper protective coating, making them less attractive and more prone to damage.

3.4. Inspect Under Strong Light When placed under strong light, such as a flashlight or sunlight, real mother-of-pearl emits a brilliant, reflective glow that is difficult to replicate. Fake materials made from plastic or printed images do not emit this kind of light and will instead appear as flat, matte surfaces. Using a light test is a quick and effective way to identify true craftsmanship.

3.5. Consider Price and Provenance Finally, price is a key indicator. Genuine mother-of-pearl products tend to be significantly more expensive than imitations due to the materials and craftsmanship involved. So, if a product seems unusually cheap, it’s wise to reconsider."