Hitler appointed Albert Speer the architect for Luitpoldfesthalle, the Zeppelinfeld Ehrentribiine, the Luitpoldarena Ehrentribiine, and the Kongressbau, “all these buildings except the Kongresshalle, which had been designed in 1933 by Ludwig Ruff. He gave me a free hand with plans and execution and participated every year in a ceremonial cornerstone laying. However, these cornerstones were subsequently moved to the municipal buildings and ground yard to wait until the building had made further progress and they could be incorporated in the wall. At the laying of the cornerstone for the stadium on 9 September 1937, Hitler solemnly shook hands with me before the assembled party bigwigs.
‘This is the greatest day of your life!’ Perhaps I was something of a skeptic even then, for I replied: ‘No, not today, my Fuhrer, but only when the building is finished.

The Fuhrer laid the foundation stone for the Congress Building on 11 September 1935.
Party Grounds view card franked with Scott 442 and posted 11 September 1936, one year to the day of the laying of the foundation stone.
For the period of the Rally, 8-14 September, the main Nurnberg post offices were provided with special commemorative handstamps for use on the envelopes and post cards presented by philatelists and souvenir hunters. The handstamp was identical to that used in 1935 except an identifying letter appears below the date bridge. All in all, 24 different handstainps were allocated, but only a few receiving post offices have been identified.
Unfortunately, “y” is unknown at this time.