It is a BCHR eyedropper with the regular safety valve operated from the culotte. It dates back, probably, from the 1930s.
Its overall condition was excellent save for the stains on the gold plated steel nib. The embossed pattern is in perfect condition and, as many a collector favor, the original price sticker remains attached to the pen. A whopping JPY 3 was the price back in the day, but sounds like a good investment. The current owner confessed having paid a lot more for this pen at a Tokyo antique fair.
The gold plated steel nib. Its engraving says "WARRANTED / 14 KT / GOLD / PLATED / MADE IN / JAPAN
My thanks to Mr. Furuya.
(Madrid, February 16th, 2011)