That is an M26. I've owned one since the beginning of the year and am very happy with it.
The M26 has the cockpit set further after, almost right up against the transom and also a slightly higher cabin to give about 5' 8" headroom. Most of them are diesel powered although some have an outboard hung from a pad attached to the transom. My one has the engine offset so the prop is on the port side which can be really annoying when reversing.
Aside from those built by Marieholm, there was at one time a builder here in Australia who was building them under license and so we have quite a few here. The Nordic is the original design (still being built today to one-design rules) but the IF and the M26 are very close variants of it, as is also the Stella. They all share in common a full keel, high ballast ratio (I think around 52-54% usually carried as cast iron at the bottom of the keel) and a tall, narrow (high aspect ratio) rig that was designed to catch the breezes up high so the boats could sail down the nordic fjords. The are known for being stiff, sea kindly and being able to carry sail in even heavy weather.
Are they good blue water cruisers? I haven't done any yet so can't answer that question. I think they could be a bit cramped for long trips. BUT there are some well known stories of people who have successfully undertaken long passages in them including Anne Gash who sailed Australia to England and return in her Stella and Blondie Hasler who did four transatlantic crossings in his junk rigged Folkboat.
FWIW, you'll find that there's a fleet of Folkboats based in San Francisco where apparently they are ideal for the local conditions.
From the photos, the ebay one looks like a really nice boat!