[Varyon]

I'll need to wait until I've watched season 2 before commenting too much (or paying too much attention; fortunately I had already heard about Ahsoka and Fett showing up but the fewer new spoilers I find the better), but in season 1 I remember his armor got pretty torn up by the big beast he stole the egg from for the Jawas. However, I'm not certain the bits that were damaged were Beskar, or if his armor prior to payment for delivering the Child had only some Beskar parts and the rest was plasteel or similar. I believe Beskar is meant to be particularly effective against energy attacks, like blasters and lightsabers - it's fully Hardened against such attacks at the least, and probably gets extra DR on top of that. It's also likely very effective armor against more physical threats.

Of course, a really important thing to keep in mind is that Star Wars - and thus The Mandalorian by extension - is a highly cinematic setting, where things like how effective armor is are dictated more by story than physics. The Smith absolutely wrecks stormtrooper armor more because she's a badass than because of a Beskar hammer trumping plastoid composite (and "Hey, this thing is capable of working a super-special-awesome material, obviously it would laugh at an inferior material" could also be in play). Something like GURPS generally calls for more concrete stats than "this is MOAR BETTAR," so you'll just need to figure out a scheme that works for you.