This is a Sheaffer gold filled flat top.  Not particularly common, these pens are most often seen as smaller ring tops but this one is a full-sized pen, measuring 12.7 cm capped.  Unusually, the gold filling has survived the 90-odd years since the pen was made in very good condition, with no brassing.

I believe this pen to be one of the later ones, after 1923, as it has a Lifetime nib rather than a number three.  Otherwise, these pens remain pretty much the same from first to last.

I’ve always liked Sheaffer’s flat tops and I’ve had quite a few over the years but I didn’t expect that one like this would fall into my hands.  They are quite exceptional.