According to this
http://i63.servimg.com/u/f63/13/33/54/62/88-39010.jpg
(from rosebreeders.org, I believe Simon Voorwinde's)
it is:
77-505 x 75-229
or
[(virginiana alba x (virginiana alba x Betty Morse)) x ? ]
X [ virginiana alba x ( Cyt. 127 x (<bracteata x foliolosa > x OP) ) ]