Interesting what Jaggy says about Atlas. I used to be impressed with their coins, until I realised where some of their copper coins come from, how they've changed colour, and their mark-ups in some cases being phenomenal.
For instance 1849 penny, sold DNW 12/12/17 £1700, stained on one side but reasonable coin. Now just sold by Atlas at nearly $6K and it's changed to a glossy dark blue colour! Obligingly slabbed of course by PGCS as MS63BN. It's still on the website but perhaps not for much longer. Check it out while you can. Amazingly enough it is the same coin.
Also, 1825 proof penny, sold Stacks Bowers 13 January $950 Lot 20358 hammer PF63 PGCS, now "blued up" and on at nearly $6K, good old PGCS again upgraded to PF64+. Distinctive die-flaw and spot on obverse, so easy to recognise.
1805 Irish silver halfpenny, untouched thankfully, now $7,500, $1600 hammer Spink Auction 339, Lot 219 14/1/2018
There are other examples on the website currently. I don't know what other people think, but the combination of huge mark-ups in some cases on the back of chemically enhancing the coin's appearance then getting it re-slabbed and upgraded, is sharp practice in my book.