The 3FN is a re-issue of the original 3F with non-rollable amorphous transformers. Nitsch worked with Doug of ECP and it is reputed to be a faithful reproduction of the original circuit. It should be more widely owned/heard since for my money it's one of the best, if not best, semi-production SS amp for dynamic headphones. It's not suitable for planars.
I own 2 because I had one for the office and one for home. Now WFH so I have one in my home office and one at my leisure chair. I'm fully done with amp shuffling since I'm also done with planars. The 3F is to my ears perfect for the HP1000, ES-R10, HD580, and the Atrium. I've also gone crazy and put silver transformers in them for the last mile improvement in holography, timbre, and staging.
Pictured is not 2 3Fs but rather ECPs unknown out of production DAC, the Walnut V, alongside the 3F. If there is anything I collect it's those DACs because he's not making them anymore and there's far fewer of them made in comparison to the 3F.