Up for sale are 7 new old stock US Military ML-635-UM Meteorological Balloons (6 still in the factory plastic bag and 1 opened for the picture). 

The stock number is 6660-00-936-8927. They are dated the March 1976. They are made of a neoprene material. The MFR is Kaysam Corp. of America Paterson, N.J.

 If there are any questions feel free to email.