More weight for better smoothing

Some time ago, while surfing the net,
I found and purchased this infill smoother. 
It has no marks on the body, the blade is a tapered one type (more thick at cutting edge) and may be is not the original iron, as these planes often had a parallel iron (constant thickness).  
The infills are rosewood, the anterior one shows evident signs of a customer repair. The iron is marked I & HSorby, the cap iron has "Dell Bros Cast Steel" on the showing surface.

I have been very impressed from its weight, 2,2 kg, although the plane was only 18 cm long. The body seems to me a single piece of steel. The iron is held in place by a rosewood wedge. It fits between the blade and the strong steel abutments.  
If compared to a wooden smoother
(1,1 kg) the weight is doubled, although the infill plane was shorter.

The performances are very good and, I am sure, the body mass, concentrated in few inches,  provides something extra.