Not sure if serious. My swords are made of steel. Just the ordinary stuff. Those in my collection all weigh between 2 and 4 lbs. It's not physically possible for them to weigh 90, not even if they were made of tungsten or uranium. By way of comparison, a typical machine gun (let's say a Bren, at 4' long about the length of a typical medium-large sword) which is a much more substantial and fairly solid piece of metal ("take a lump of steel and mill away any bits that don't look like a machine gun", as someone described its manufacturing process) weighs 20 lbs. I also have one of those behind me. I would consider it essentially impossible to swing at someone with any hope of hitting them considering the enormous amount of inertia.
ISTR actual martial arts practitioners suggesting that the cut-off point between something being usable and just being an ornament is about 6-7 lbs.
