Decorative certificate, apparently an award to Mr. Van Grunderbeck, for his work in decorating and illuminating a facade for the celebration in July 1890.
Based upon my limited research, there was apparently an organized effort to revive this quarter of Bruxelles, which began in 1888. The striking "Diplome" was apparently given by the Commitee in appreciation for the work done by Mr. Van Grunderbeck and is signed by both the President and Secretary of the Commitee.
The includes a number of decorative coats of arms and a marvelous allegorical scene, which incorporates the Lion of Belgium and a Globe, among other embellishments. We truly have no idea what the value or importance of the item may be, but could not resist the decorative chromolithographic images.