I visited this WHS in June 2018. Apart from the falun red earth-and-timber furnace with engraved milestones (photo), the other components of this WHS are quite similar to the agricultural and idyllic setting of the decorated farmhouses of Halsingland rather than part of an industrial landscape.
The ironmaking traditions of the Norberg mining district go back to the Middle Ages even though iron had been worked at Engelsberg since prehistoric times. In summer, guided tours can be pre-arranged everyday by contacting the tourist office in Fagersta, but make sure to have some kroners as only cash is accepted (very rare in Sweden!). The area can be easily visited for free without a guide by following the numerous information boards. To me, the highlight of this WHS was the area around the manor house with the clock tower, two ornamental slag-stone towers and the nearby forge powered by waterwheels.
Opposite the ferry point to the world's oldest preserved oil refinery on Oil Island, make sure to visit Nya Serveringen, an excellent place to have some shrimp skagen and freshly baked pastries. All in all, the WHS in Engelsberg was a worthwhile picnic stop en route to Falun.