I had an Iwasaki no 90 identical to the one you won!...a bit more use on it then this one but otherwise identical.

It was an exceptional shaver.

Blade @0,5 -1cm shorter (I cant recall exactly but I think 2,5 inch-ish) then a regular size iwasaki....a no.50 for example is regular size @3inch cutting edge.
If I remember corectly the no 30, 60 and 90 are made a bit shorter to make them easier to sharpen by lady barbers....some are even found with the marking''Lady'' on the tang or the kanji meaning the same thing.

They are quenched horizontaly like a katana and you have to keep in mind that only 2/3 of the blade is actualy hardened....the 2/3 at the cutting edge...the spine is left soft-ish and I recomend if you always use a layer of tape when honing it.

If you ever decide to etch it...and I doubt you will...it will show a nice diferential heat treatment line.

I would box it and use it on special ocasions... blades like this rarely pop up...and over the years they will be even rarer.

Enjoy it!