More than once Rembrandt painted armour for the sake of the effects of light.
In one of the portraits of himself he wears a helmet, and he painted his brother similarly adorned.

A picture of a person wearing the same armour as in the Glasgow picture is in St.Petersburg, but the figure is turned in a slightly different direction and reflects the light differently.

It is called 'Pallas Athene,' and was no doubt painted at the same time as ours; but the person, whether named Pallas Athene or knight, was but a peg upon which to hang the armour for the sake of the light shining on it.
Rembrandt was a typical Dutch worker all his life.

Besides the great number of pictures that have come down to us, we have about three thousand of his drawings, and his etchings are very numerous and fine.
I wonder if you know how prints are made?
There are, broadly speaking, two different processes.

You can take a block of wood and cut away the substance around the lines of the design.