Swan chair  

Yes, the version with...
Yes, the version with Casters was made to be used as a desk chair. Simon has one too withe the following description
"Stunning Danish design classic swivel chair designed by Arne Jacobsen.
Swan designed in 1958
Produced by Fritz hansen
Model 3324
Year of production 1976
This rare version of the chair as a desk chair is both functional and elegant while being an icon of all Danish design.
The chair is upholstered in the original 1976 black leather and this has aged extremely well with a wonderful patina and soft worn look which is far from worn out or damaged.
The chair has height adjustable stem which allows the user to adjust it to acheive the best working height.
The dye-cast aluminum base has the original castors which are all in perfect working order and undamged.
The chair bears the original FH label with 1976 and is in general one of the most impressive original chairs I have seen."
http://www.christies.com/lotfinder/LotDetailsPrintable.aspx?intObjectID=...

thanks jesgord.
It feels pretty hard. I assume there is phone underneath. Is it supposed to be a cushioned feel or is the hardness the norm? Sorry for all the questions, very unfamiliar with the chair.

If its old, the foam has...
If its old, the foam has probably hardened...and then it will begin to crumble. Eventually, it will need new foam and to be reupholstered. Even then, though, it will never be a "soft" chair.

Swan chair is upholstered in...
Swan chair is upholstered in a wide range of fabric or leather. It spins at its chrome base and is available with an automatic return mechanism. The Swan chair was designed, along with the Egg, the two-seat Swan sofa by Danish architect and designer Arne Jacobson in 1958.
http://www.regencyshop.com/p75/Swan-Chair/product_info.html