Yes, a demonstrator pen is pen that is clear/translucent so you can see the inner workings of a pen. The neatest ones are the Pelikans as you can see how the piston mechanism works.
If you go with a Sailor (or Pelikan ) check with Pam Braun at http://www.oscarbraunpens.com/ she and Todd at Isellpens have some of the best prices around, Pam also sells inks at good prices.
I really like sailors, I think their nibs are better than Pelis, but the pelikans hold much more ink than the Sailors per fill.
If you go with a Sailor (or Pelikan ) check with Pam Braun at http://www.oscarbraunpens.com/ she and Todd at Isellpens have some of the best prices around, Pam also sells inks at good prices.
I really like sailors, I think their nibs are better than Pelis, but the pelikans hold much more ink than the Sailors per fill.