Thank you for the reply Brady,Baltic Birch aka Russian Birch comes from Russia or Scandinavia. Most of it comes in as plywood. Tried checking my sources for more information and could not come up with more than this so far. I have not seen any sources for just the wood.
It should make a decent pen, the wood is reasonably hard and I have made many pens from softer woods. The issue will be with the plain nature of the grain, would not be very interesting unless you use a knot or burl piece. Even then I seem to remember that there is not a very distinct colour difference between the summer/winter ring zones of the grain.
That's definitely a better choice I would think, much more interesting to look at! Thanks for that. I will run that byWould Masir birch from Norway be a suitable alternative? It has a very interesting grain pattern. It is also fairly easy to source for pen blanks.