1964 AD., Belgium, Baudouin I, Banque Nationale de Belgique, 20 Francs, P-138a.1. 2 H 0588332 Reverse

State: Belgium, Royaume de Belgique - Koninkrijk Belgie
Issuer: Banque Nationale de Belgique, (Belgium), Trésorerie - Thesaurie
Location of issue:
Date of issue: 15.6.1964 AD.,
Value: 20 Francs
Size: 118 x 59 mm
Material: paper
Watermark:
Serial : 2 H
Serial no. : 0588332
Signature: Marcel d'Haeze (1)
Printer: Banque Nationale de Belgique, (Belgium)
Obv.: 20 / ROYAUME / DE BELGIQUE / TRESORERIE / 2 H 0588332 / VINGT / FRANCS / 15.06.64 / …. , bust of Baudouin I facing.
Rev.: 20 - 20 / KONINKRIJK BELGIE / THESAURIE / TWINTIG / FRANK / …. , Atomium in Brussels.
References: World Paper Money P-138a.1 .

The Atomium is a landmark building in Brussels (Belgium), originally constructed for the 1958 Brussels World’s Fair (Expo 58). It is located on the Heysel Plateau, where the exhibition took place. It is now a museum.
Designed by the engineer André Waterkeyn and architects André and Jean Polak, it stands 102 m (335 ft) tall. Its nine 18 m (60 ft) diameter stainless steel clad spheres are connected, so that the whole forms the shape of a unit cell of an α-iron (ferrite) crystal magnified 165 billion times. Tubes of 3 m (10 ft) diameter connect the spheres along the 12 edges of the cube and all eight vertices to the centre. They enclose stairs, escalators and a lift (in the central, vertical tube) to allow access to the five habitable spheres, which contain exhibit halls and other public spaces. The top sphere includes a restaurant which has a panoramic view of Brussels.
More on https://en.wikipedia.org/wiki/Atomium