Proof ½d. complete design in black and blue, stamp size and affixed to piece (87x34mm.) marked ''Appd for die'', initialled and dated ''20/2/34''. Photo.

Recommended features

• • 

  • ‘Wow — that’s Judd!’: How the father of Minimalism came to revisit and embrace colour

    This March sees the first US retrospective of Donald Judd in 30 years, revealing aspects of the artist’s practice that may surprise those who think they know it well

• • 

  • What to look for on the back of a painting — an expert guide

    From labels and staples to stretchers and repairs — the reverse of an artwork can reveal more about it than you might suppose