In GURPSage, those are Duelling bucklers.
Ye olde Viking shields are pretty much a duelling buckler with a light wooden rim; if the wooden part gets hacked to bits, you still have the little buckler.
Viking swordplay is axe-derived; they tended to "fence" with their shield far out in front, with the sword held back until it swings in for a big chop/slice. English style swordplay is spear derived; sword out in front, with the shield just behind it, fencing with the swordpoint.
The English style works well with a strap-on shield, the Viking style wants a buckler.
Ranar's current shield is a Heavy Medium shield with a spike.
The big Roman shields were technically bucklers as well; they were too awkward to strap on.