Sweden, and in the case of not knowing you were dealing with stolen goods but still found guilty it seems the worst case scenario is six months in prison. [1]

[1]: https://lagen.nu/1962:700#K9P7S1 (Text in Swedish.)

This wasn't always the case, but I can't quite remember when the law changed. It used to be that you could claim you bought the goods "in good faith" in which case you'd be free of liability unless there were other hard evidence to connect you with the crime – even if you bought that high-end watch off of some dude selling watches on the street out of a cardboard box.

These days however, it's much easier to convict someone (whether selling or buying) because of a clause that includes anyone who didn't know but had reason to believe the goods were stolen. It's easier for the prosecution to prove the latter, and probably gets rid of most "it fell off the back of truck" arguments. That high-end watch from that shady dude on the street would probably get you a fine these days. (Putting people in prison is costly, after all.)

No. If you bought a high end watch from a shady dude well below market price and without any papers, you could be found guilty of a crime (posession of stolen goods) before the law changed as well as after the law changed. Nothing has changed there.

However, if you bought a used watch at a reasonable price with some plausible documentation, this is where things has changed somewhat.

Before, if you had bought the watch in "good faith", i.e. there was no obvious reason for you to suspect it was stolen when you bought it, you were entitled to keep the watch even if it was later found out it was indeed stolen. Even if they later found the previous owner, he wasn't allowed to have it back. He had to go after the thief to get compensation (even if the thief is unknown).

That last thing is what changed. If they find out the watch is indeed stolen, you have to give it back to the previous owner, even if you bought it in "good faith". But you have not committed a crime, you will simply have to give back the goods to the right owner. Now it is you as a buyer that has to go after the thief for compensation (because he scammed you by selling stolen goods).

I suppose you already know about §259 StGB in Germany.

(up to 5 years for handling goods that were stolen by somebody else)

I am not a lawyer nor a German, but Wikipedia says that German law has no strictly liability [1], which would seem to imply that knowledge (or at least belief or a willful lack of knowledge) that the goods were stolen would be necessary to prosecute that crime. Is that wrong?

[1] https://en.wikipedia.org/wiki/Strict_liability_(criminal)

You are right in your assumption. § 259 requires intent. Usual interpretation is that the offender needs to know the fact that the good was somehow acquired illegally (but doesn't need to know any details). It's not enough to think of a possibility of such an action, they have to resign to the fact. (There are other obligatory characteristics that need to be fulfilled, but they are irrelevant to this discussion.)

Simply handling stolen goods is not a criminal offence in Germany.

Netherlands too: if offered a deal which seems too good to be true....

edit: criminal liability indeed