The KrooKs pen is a 'no nonsense' German piston filler dating from the 1960s. This example is in near mint condition.
The pen has a handsome 14Ct. Gold No.5 ERO nib, it writes with a nice amount of flex.
The piston filling mechanism is in good working order, taking up a good volume of ink, very similar to the Pelikan arrangement.
I have sen very similar pens branded as ERO but they seem to have gold plated steel nibs, rather than solid gold as in this case.
It may suit someone looking for a low cost pen to hone their skills using a gold flex nib.