The Oxford Companion to German Literature describes Harro Harring (1798–1870), revolutionary, writer, and painter, as ‘a stormy petrel of 19th-c. demagogy, [who] took part in the Greek War of Liberation in 1821, travelled restlessly in Europe, and in 1828,’ having been inspired by meeting Byron earlier in the decade, ‘was for a few months house dramatist in the Theater an der Wien, Vienna. Later in that year he obtained a commission in a Russian guard regiment stationed in Warsaw, but returned to Germany when the July Revolution broke out in 1830. Over the next twenty-five years he was repeatedly expelled as an agitator from various German states, from Switzerland, from Norway, and from Denmark. His points of rest were the USA, South America (Rio), and London.’ His final years he spent in exile on Jersey, before finally committing suicide in 1870.
Another point of rest was evidently Hull, from where he wrote this embittered open letter on 29 November 1850, calling for his fellow republicans in northern Germany (Harring himself was from North Frisia) not to be subservient to Prussia. Harring was at the time promoting a pan-Scandinavian union of free states, for which views he had been banned from Norway just months before.
I cannot find any German printing done in Hull in the nineteenth century, so perhaps this was actually printed in London. It would certainly be interesting to compare the type used with contemporary German radical printing emanating from London. It is not dissimilar to the Fraktur used by J. E. Burghard for the Communist Manifesto in 1848.