Brüko is a German Instrument maker founded in 1890 in Rothau, Bohemia and originally producing Violins. Over the years they added other instruments and in 1932 they started making Ukuleles and Banjos. After WWII the company was built up again in Eltersdorf near Erlangen and in 1990 the company moved to Kitzingen. 

Today they are still in business and still in Kitzingen. They produce ukuleles of all scales from Soprano to Baritone, (though the Baritone is a custom order), plus soprano pineapples with 12 frets to the body, and 15 fret Supersopranos and Supersoprano Pineapples. They also toyed with Sopraninos in 2010 but they only made 3, however they no longer make Violins or Banjos, (though they do still make sound posts for Violins). The Brueko spelling of their name is often used outside of Germany because people can't find the ü, (or u with umlauts - alt+129). 

The Ukuleles they make are all solid wood and these days primarily mahogany and maple, but they do use other woods, both for the regular models and the special runs. Brüko ukuleles have very little branding on them, sometimes a sound hole stamp, sometimes just a made in, (West - during that period of history), Germany, but they do usually have a distinctive wooden bridge and saddle design. They are also quite fond of making the thin bodied "travel" or an arched back, no rear bracing designs.

Over the years, in addition to making their own branded instruments they have acted as OEM for a number of companies including Hilo, Boosey & Hawkes, and Hofner, plus I'm sure others. In fact another firm they made instrument for was a distributor in Schaffhausen, Switzerland called Alfons Marcandella who branded them Alma (AL-fons MA-rcandella). Thanks to Alex Mueller for this information