by day's end, thanks to some leads from colleagues, the scan reached Yvonne Mounsey in California - as she created the lead of this pas i suspected it might be she in the picture, but could not say so confidently (my dance-watching days of NYCB post-dated her career there) eventually, the following communication came from a young woman working with Mounsey these days, who has email and who thus had the photo on her screen for YM to comment on.
here's what Mounsey said to her freind with the email:
(Looking at the photo, dancers from left to right:)
Arlouine Case / Kaye Sargent / (Helen Kramer?) / Barbara Milberg / Yvonne Mounsey / Ann Crowell / Una Kai / (?)
even after looking at a higher resolution scan YM said she couldn't identify the two question-marked dancers.