The list of works of the Kondor (1912-1954) gives 1028 different commissions executed. Keeping all the drawings of all the executed assignments did not seem to make much sense: many assignments were (and are) of interest neither for architectural nor for (concrete) engineering history, and the documents of those projects will therefore provide us with little information (in that respect). It was decided to carry out an "administrative selection" based on a number of criteria. Projects were selected which:-form highlights in the development and application of concrete technology;-are or were of some importance in the development of civil engineering (here a less strict selection was required because -as far as is known- so far little of this material has been preserved);-form highlights in the history of architecture (and then in particular with regard to the influence that the use of concrete had on the design);-are/were of importance for the history of the company.This administrative selection was done by:-Prof.ir.J.Oosterhoff: history of building technology (especially civil engineering works);-Ir.C.van Eldik: history of building technology (especially history of concrete technology and application);-Drs.J.P.Baeten: architectural history (with emphasis on concrete applications);-J.C.den Outer: history of the company.Furthermore it was decided:-to keep all the photographs. This is a unique and particularly accessible collection of photographs of buildings and construction work from 1912-1950/'60. Only the documents to be preserved were then transferred to the NAI and will be managed there in the future and made available for research.