But since stanza 21 names the duchy of Milan as in league with the Confederacy, that portion was likely written earlier, in 1474 or 1475, as duke Galeazzo Maria Sforza also entered a pact with Burgundy in 1475, lending it military support against the Swiss, much to the discontent of the Confederacy, so that a Swiss poet writing in 1477 would probably not have mentioned Milan as an ally.
[1] The earliest record of the poem is in a manuscript written by Ludwig Sterner in 1501, where it has the title von der eidgenossen pundt "of the pact of the confederates".
The text was printed for the first time in 1545 by Augustin Fries under the title of Ein hüpsch lied vom ursprung der Eydgnoschaft und dem ersten Eydgnossen Wilhelm Thell genannt, ouch von dem bundt mit sampt einer Eydgnoschafft wider hertzog Karle von Burgund, und wie er erschlagen ist worden.
[3] The first 14 stanzas explore the foundation and growth of the Old Swiss Confederacy, the expulsion of the foreign bailiffs as well as the story of William Tell.
The account includes Tell's apple-shot, his admission that he had reserved an additional arrow to shoot the bailiff in the event of his killing his son, and his escape, but not his eventual assassination of Gessler.