The Nahvalar pens - and I have three of them - are beautiful. I am an engineer and they are also extraordinarily well crafted.
I love Nahvalur jade. It looks fab in the Narwhal Spring pen!
It writees nicely out of the box but about 10 minutes with some micro sanding sticks and the medium writes like glass.
I have an Asvine P20 and wanted a stub nib. The Nahvalur nib/feed is interchangeable. I could not find any in AUS so ordered from US. Then postage you charge is prohibitive so I had it posted to a Friend in CA who then used USPS to sent it to me in AUS. NOTE: We are taking about a nib/feed NOT a complete Fountain pen so much of the response are meaningless.