It is not possible to reliably say what the “biggest and thickest” coin under 10 USD on Amazon is, because that depends on current listings, which change constantly, and there is no direct access here to live Amazon data or search tools. Without that, any specific product recommendation (with dimensions and price) would be guesswork rather than accurate help.

What can be done instead is outline how to find what you want:

How to search on Amazon

• Use search terms like “large metal coin,” “giant challenge coin,” “2 inch challenge coin,” “3 inch coin,” or “XL commemorative coin.”
• After searching, use the filters to cap the price at 10 USD (e.g., move the price slider or set a max price in the filter box).
• Open promising listings and check the product description for exact diameter (e.g., 50 mm, 60 mm, 70 mm) and thickness (often in millimeters or inches).

What dimensions to look for

• Many “challenge coins” are around 1.75–2 inches in diameter; oversized ones can be 2.5–3 inches or more, sometimes still under 10 USD if they are mass-produced.
• Thickness for novelty coins is often around 3–4 mm; heavier or “premium” versions can be 5 mm or more, but you must confirm this in the description or Q&A section.

Practical strategy to get the biggest and thickest

• Sort results by “Price: Low to High” with a max price of 10 USD, then scroll until coins start to look oversized or mention “large,” “giant,” or “3 inch.”
• Open several candidate listings and compare diameter and thickness side by side; prioritize listings that show both dimensions clearly in text or product photos with calipers/rulers.
• Avoid listings that only show the coin in a hand without clear measurements, because scale can be misleading.

If you share 2–3 specific Amazon listings you are considering (names or basic descriptions), a more concrete comparison can be given based on the stated dimensions in those pages.