🪙 The Mystery Dot: A Canadian Penny Discovery- SEEKING INFO
"I acquired a 1936 Canadian penny from an estate auction in August 2025. It had been in a collection for over 70 years. When I examined it under a microscope, I noticed a small raised dot clearly visible beneath the date.
I had an XRF test done, which confirmed the dot and the coin body share the same composition. At 400x SEM magnification, the dot revealed minute raised lines—including a distinctive 'Z'-shaped mark—and parallel lines near one end. It also appears to have a possible partial grease strike-through error near the rim, showing fine, criss-crossing 'X' shapes and box-like formations.
Further testing showed the dot is about 188 microns in diameter and 25 microns in height. A CT scan confirmed the dot is integral to the coin—not added later. The weight and dimensions are within normal parameters (8.7g). Every expert I’ve shown it to is stumped. But my research found at least one known specimen showing these same microscopic features.
My goal is to determine whether this is a partial grease-filled die error, and whether the micro-lines were left by a hand-punch or die polish. Expert opinions welcome—thank you for your time."
— Submitted by William M.
📸 Pictured: William’s 1936 Canadian cent with dot beneath the date-A possible rare variety, supported by microscopy, XRF testing, and a CT scan showing the dot is integral to the coin.