My local hardwood supplier sells sheets of 3/4 Baltic Birch in two sizes - 4x8, and 5x5. Yesterday, I just happened to ask if they both came from the same place, and -- much to my surprise -- they don't. The 5x5 sheets are supposedly true Baltic Birch, from Russia. The 4x8 sheets are imitation Baltic Birch, from China.
I'd just bought a 4x8 sheet from them a couple weeks ago, but haven't used it yet. I went ahead and picked up a 5x5 sheet while I was there, to compare the two. They are both sold as 3/4 thickness, but the 5x5 sheet is only about 15.5mm thick, while the 4x8 sheet is 18