[Marco Tahtaras]

The first latch was obviously used before traditional dovetails were used on open models. The drawings for the 30+ associated parts for the dovetails (including the latch redesign) were done 4/4/28. From that my best estimate is that implementation began about the end of April.

We know from the post on windshield finger clips that the third latch came into play late November 1928.