A single stamp in the nominal of 150D and perforated 11.5 was issued on November 7th, 1958.
Here is the mint stamp from the top right corner.
Here is the cancelled to order stamp.
Postally used specimens are, as usual, very hard to find. Here is a piece from a package wrapper that features two of the Engineering Exhibition stamps.
Ana another single postally used sim off paper.
Mixed franking of the 50D Defense of Country value together with the 150D Engineering Exhibition stamp for an overall postage of 200D on a postcard to Czechoslovakia.The cars was most likely sent by a member of there Czechoslovakian Embassy as members thereof had access to service stamps.
Registration Nr. 100140