Please Help Identify The Problem With This Coin (Undated Mercury Dime)

Your coin has most likely suffered from direct application of intense heat - a blowtorch, or something similar. This causes the surface of the coin to melt and ripple in this fashion.

Heat damage, PMD. Only worth silver melt value.

to the CCF

With above, PMD (heat damage). @Cybereyes

to the CCF Not heat damage. You can't heat the surface of the coin up to the melting point to where it puddles and not effect the middle of the coin. Especially a coin the thickness of a dime. To me it looks like it was sandblasted with glass beads. Beads wouldn't take very much of the surface off like sand or silicon carbide. The face on the obverse and the fasces on the reverse is where they held it so this area wouldn't get exposed to the beads.

First look I thought acid damage too. With a blow torch or high heat don't you get toning and the coin turns colors?

My problem with the "acid" theory is: which acid does this to coin silver? The usual culprits (hydrochloric acid, coca-cola etc) don't dissolve silver, so shouldn't show this effect.

I've seen blowtorched coins posted on the forum before that look exactly like this wavy pattern. Here's Coop's image of a blowtorched cent:


The explanation of the high points knot showing the damage is simple enough: the coin re-entered circulation for a while (or became someone's lucky pocket piece, or was simply buffed down with a polishing cloth) after being torched. The wear patterns on the cheeks and on the fasces look normal enough. Any "blowtorch colors" would also be removed the same way.

A weight might help discern the difference with more certainty; a coin this badly acid-etched should be severely underweight, while a blowtorched coin shouldn't have lost much if any weight.