de Koo was one of the most important of all PTT employed designers. He started as an interior and book designer, but soon after found his way into designing for the dutch postal service PTT. PTT has a long standing history with the best designers in the Netherlands. Schuitema, Piet Zwart and also de Koo have had their history with PTT.
( Piet Zwart designed HET BOEK VAN PTT, available at www.ftn-books.com)
de Koo designed some of the most iconic of all PTT designs. Among them letterboxes, printed matter, labels and signs.
The Gemeentemuseum Den Haag had a special exhibition on de Koo in 1988 and with it a very nice thini catalogue was published for this occasion. The book was originally published in 400 copies, but there was no interest in this publication and at the time the Berlage building was renovated , all of the remaining copies were destroyed. My guess is ther are some 100 copies being sold over time, making this one of the rarest of all Eighties publ;ications of the Gemeentemuseum and i now have an excelent copy for sale at www.ftn-books.com