I have a couple of other pens from the same era, and they have a silver looking nib, but when you take the nibs out they are gold wit a chrome looking tip.
但拆不下啊
我找到了:http://www.parker51.com/versions.html
NND, 51真出过钢尖的。
In 1950, Parker introduced the "51 Special", a lower price alternative pen, with a steel nib and shiny polished cap with a black jewel. The "51 Special" can be found in all the standard aerometric colors, except Plum.