What's up with this coin?

[Nordle11 564]

Trying to figure out if this was a pre or post mint..

It looks like it's been dipped maybe, but there aren't any other signs of this.

Opinions greatly appreciated as always.

[Nordle11 564]

Obverse

[Nordle11 564]

Close-up

[copper123 1,500]

sandblasted at an angle with high pressure sand or something else for a very short time?

[Nordle11 564]

That's food for thought, actually.

It's always good (not to mention fun!) to try and replicate post mint errors, even just to understand how they come about.

But I have no idea where I'm going to get a sand-blaster to test that theory

[PWA 1967 2,142]

Not got a clue ,maybe coppers is right and makes sense.

Horrible coin though.

[Gary D 76]

I'd have said acid dipped

[Nordle11 564]

Not got a clue ,maybe coppers is right and makes sense.

Horrible coin though.

Of course it is, but it's an error coin, not one for the main collection

[PWA 1967 2,142]

Not sure if its an error mate if its post mint.

[Rob 3,152]

corroded and cleaned

[Nordle11 564]

Not sure if its an error mate if its post mint.

No certainly not, that's what I'm trying to ascertain though.

I do have some pennies with post mint 'detailing', we shall call it, but they are a small side section and mainly things like nicely engraved coins or things as such.

[VickySilver 832]

I concur with the acid and have seen very similar effect when high molar acid is used (e.g. nitric, hydrochloric) and there is a more pronounce "boiling" effect of metal off the surface.

[Rob 3,152]

I has to be chemical. The legend shadowing is an expected result from acid based corrosion. The legend by definition involves a change in relief, i.e. you have metal flow to produce it, which will result in metal stress faults where the crystalline structure has been stretched. This will allow any acid to penetrate deeper and so result in a depression around each letter as the acid works more effectively in the stress faults.

[Coinery 1,157]

There are some great acid images somewhere on this forum for comparison. They all show the increased erosion upon the stressed metal around the devices, as is mentioned above.

[Nordle11 564]

Thanks chaps, and as always, thanks to Rob for a great explanation.

I'll have to dig around for these pictures for comparison, thanks!