Probable Struck-Thru Cloth 1949 Nickel

It weighs a normal 5 grams.

After UNUM Looks interesting. But not part of the design for a nickel. Struck through cloth doesn't leave the devices that sharp:



Opposite side not affected.

Here is a interesting thought. Could it be a planchet error like an annealing flaw that happened before strike? Of course, nick10 could also be right.

maybe before an acid bath it weighed 5.1 gr

with nick10.

"5 grams" is too imprecise to say much. If we are talking plus or minus a gram for the lack of precision of the scale, that is ~20% material loss! Even at plus or minus a tenth of a gram, I would not be confident in ruling out an acid bath. If the acid attack were uneven, 0.1g of material loss on such a small surface area might look pretty obvious. While it isn't with US coinage metals/alloys, I have experience measuring metal loss due to corrosion or intentional etches prior to other surface treatments. Visible changes can be difficult to measure with a $2000 analytical balance, even with measuring test coupons which were weighed before and after the damage occurred. What chances do we have at a definitive conclusion when the exact initial mass is not known, and the final mass is measured with something like a $20 consumer model scale like I have at home?

If the OP had reported a mass of 3.5 grams, we might take that as evidence of material removal, because that is so far outside the expected range, even allowing for mint tolerances. But, this is one of those cases when our methods of observation and measurement tools are not always capable of proving something in the negative. I am not saying that the coin has seen an acid bath, I am just saying that the weight cannot disprove that. The pattern on the back puzzles me, but the irregularities on the obverse looks much more random. I think nick10 has an interesting and plausible hypothesis.

I picked up this nickel in Galesburg, MI at an antique mall from a coin dealer several years back. When I first saw it, I was thinking it looked like a struck-thru cloth error. It was in a bowl of mixed coins for a set price.

Hey Mikediamond, thanks for that great possibility of what this is. As my username implies, this is a legit what-is-it, error/pmd style. Something I never thought of. Lol, cloth was still involved apparently...

I do use error-ref.com often when I need it.
This is one of the strangest oddities on a coin I have ever seen, mint-made or not.
Now it also makes me wonder who would have wanted to do this?