Henri Selmer & Cie. was started by Henri Selmer in France in the 1885 making Clarinet mouthpieces and reeds and by 1900 had expanded to make the whole Clarinet. The Clarinets were a success internationally and in 1919 the firm had expanded its range of instruments and moved to a much larger factory in Mantes, having already in 1909, started firm in the U.S. (H and A Selmer), under Henri's brother Alexandre. In 1927 after a period in partnership with G.C.Conn, H and A Selmer became a fully independent company with a licencing deal to distribute Selmer instruments in the US. In 1928 an Englishman called Ben Davis started a UK branch of Selmer under a similar licence this branch of Selmer expanded to become one of the biggest UK musical instrument firms at the start of WWII. None of these various Selmer firms were involved with Ukuleles, though the French firm did work with Mario Maccaferri for a while between 1932 and 34 to develop the Maccaferri - Selmer Guitar, (It is worth remembering Maccaferri was only involved with the D hole "Grande Bouche" Guitar and the later oval "Petite Bouche guitar is a pure Selmer design). 

In 1953 Davis with his brother started MPI, (Musical & Plastics Industries), as a holding company for their Selmer interests and a new firm the called Selcol as a plastics division and 'Toy' arm making garden furniture, models and other toys, including Ukuleles. 

With the Ukuleles they made Soprano, Mini and Baritone scale models and are particularly famous for the models that were part of the marketing for popular artists of the time 1960's. They must also have been working to some extent with Maccaferri and a number of their instruments are identical, (apart from the "made in England" stamp) Examples I have seen are The Beatles, Elvis Presley, The Monkeys, The Rolling Stones, Tommy Steel, Sooty (the UK children's glove puppet), and Yogi Bear, but oddly enough I've never seen the Mickey Mouse one they so obviously had the moulds for, (unless they were making them for Mattel)?
Its worth remembering that some of these endorsements can significantly increase the value of the Ukulele, The Rolling Stones on the front increases the value more than tenfold, the Beatles or Elvis seven or eightfold. Sooty or Yogi doesn't increase the value much though, and Tommy Steele probably decreases it!

They also has a number of generic brands like

• The Colombian

• Melody Maker

• Skiffel

• Skiffle Junior

• Teen Time

• Trad Jazz Special

• Club 4

Some of the Baritone scale instrument were originally made for 6 strings, (they did make plastic Guitars as well as Ukuleles), but Selcol just changed the nut and, (sometimes), the bridge, putting blanking plates over the extra tuning peg holes.

Plastic production, so Ukulele production ceased in 1968.