Short answers, pulled from the story.
The year 985 marks the first clear written mention of a Norse lething. Skaldic courtly poets praised Jarl Haakon of Western Norway and his son Erik for summoning ships to fight at the Battle of Hjörungavágr against a Danish fleet.
It took about 160 farms to supply a single ship and its full crew. Each lid contained four farms or hemman, and each Skipreide consisted of 40 lid units.
Most members of a Leidang remained unarmored during the Early Medieval Period. Wealthier men might wear gambesons and spangenhelms while the very wealthy donned mail.
This fiscal obligation persisted until the 19th century in parts of Scandinavia. The leiðangr evolved into a tax paid by all free farmers during the 12th to 13th centuries.
Norway counted 279 such districts in 1277. Denmark maintained two to three times that number.