Vintage Hansen 3217: Remove armrests?  

I finally found a vintage Hansen 3217 swivel chair in good condition – and have a few questions:

There are no additional stabilizing tubes under the seat. Does that mean that this is a very early model? Could someone estimate the year?

In my current application the chair would work better without the armrests. Would it be possible to remove the armrests temporarily without permanently damaging the chair? The metal cover is fixed with four nails, so I would see the construction if I removed it, but I don't want to do that if it doesn't make sense anyway.

I'd like to use the chair on parquet flooring. Are there any soft replacement rollers available, or can the original rollers be coated? (Of course I want to keep the original castors.)