The set of first day covers is split into 2 sections per issue.

The first set of stamps has two official cachet types of cover, the first one and most known is the one from issued by Campo Rodan. Campo Rodan was the so-called official FDC cachet editor on the belgian market. The design of the cachet will also be issued by many different countries and organisations during the World Fair (see Belgian Cancellations).

The second cachet was issued by Grumiaux, less known.

The Campo Rodan design was based on the set of three belgian colors of the belgian flag (black, yellow, red) and cancelled on day of issue being 17 April 1957. :

The Grumiaux Cachet type:

That day, Campo Rodan has printed other covers with similar design but with the title FDC:

Another cachet have been issued by some instance in Eynatten (near Belgian-German border), which is shown below:

The stamps issued on 4 February 1958, were cancelled on two Postal Offices: 1C and 1R. The use of the letter R is confusing. Based on available information, the only letters available till April 1958, were letters A to E. Other letters among them the letter R, were only available as from April 1958 (2 months later)... Cancellations with the letter R, are probably rarer to be found ?

Cachet of Campo Rodan cancelled on 1C and 1R. The following cancellations are known: 1B, 1C, 1E and 1R

Some covers were issued without the yellow color and which are rare and with the 'normal' Brussels cancellation:

A cover was also edited by Grumiaux (cancelled 1R):

 Other more difficult to find, first day cancellations, like the one of Antwerp below:

 Finally, a FDC cover of Grumiaux, but not cancelled on 2 April 1958, but on 8 April at 1E, and addressed. This can be seen as the FIRST cancelled cover for normal postal use with the Brussels Exposition cancellation (prior to the official opening of the exhibition on 17 April 1958:

Another unusual cancellation is from Brussels 1 official Postal Office: