https://www.error-ref.com/tapered-planchets/ Here is a recent addition to my collection I acquired from my local coin dealer. An almost text book example of a tapered planchet, close match to the one shown at error-ref.com. Thin from 2 to 5 k. Obviously pulled from circulation. It weights in at 2.80 grams, with an edge that is visually thinner. It was in a older 2X2 with a square view window. If any one know the vintage of this type of holder I would be interested in knowing. It has two separate sheets of clear plastic glued to the cardboard at only one edge. Thanks for looking. The 'N' in United is bolder than the letters around it. Just an odd abnormality. Feel free to post any similar error coins or info on 2x2 holders.
I believe you can still obtain the square 2x2s. They come in a variety of shapes, even oblong for those rolled coins.