Window Pane Gray Pearl Sheaffer Balance Statesman fountain pen - fine point

I describe Balance pens like this one as window pane barrel pens. The pens have 2 wide panes of clear celluloid on opposite sides of the barrel. The panes on this pen have ambered but they still allow easy viewing of the ink level. The window pane pens seem to have been made primarily in the last couple of years of Balance production which ended in 1941. I believe that is true because all those I've restored have celluloid covered, carbon steel filler rods but also price codes. These rods were made in the earliest Vacuum-Fil Balances in 1935 before Sheaffer switched to using stainless steel rods. The price codes (this pen is stamped 1000 below the manufacturer's imprint on the barrel) were introduced in 1938. So, this is a post-1938 pen with a pre-1936 filler rod. I believe that wartime shortages of stainless steel forced Sheaffer to revert to using the celluloid covered carbon steel rods. I've replaced the filler rod on this pen with one custom made from black oxide coated stainless s