Yangjia Michuan Taijiquan Study Aids
Here is a link to a document that could be helpful for students who are learning and practicing the 13 postures of the Yang Family Hidden Tradition: 13 postures YMT Introduction .  And a Link to a nice video featuring Nicole Henriod, a french YMT teacher, demonstrating the 13 postures of the Yangjia Michuan form. For video relating to all aspects of the Yang Family Hidden Tradition you can click HERE.

UPDATED August 16, 2015: Here is a link to Wang Yen-nien demonstrating the first section (first duan) of the Yangjia Michuan Taiji form. It was recorded in Taipei, where he taught and lived. It is said to be from 1987 – it seems like it could be earlier to me. Regardless, it is a valuable view of the form as he taught and practiced it:

UDATED May 13, 2016: And below is a link of George C. Lin, a disciple of Wang Yen-nien. Many members of Robert Politzer’s original class circa 1993-2001 were able to meet and to study with him in Europe and in the states.