NOTE: Because the Reading Eagle listed this as "Oscar's Balance Beams" I assumed that was correct. I have now learned it was Bert's Balance Beams and also sometimes listed on signage and printed materials as Bert's Balance Boards.
Recently we looked at this picture and guessed that it was Bert's Balance Beams:
Image from Photobucket
A 1983 Reading Eagle article mentions this play element, but refers to it as Oscar's Balance Beams:
Oscar's Balance Beams provide a chance for skillful adventurers to make their way across the balance beams over gentle geysers of water.
Here is another photo I found:
Image from Picasa
This photo shows the "gentle geysers of water" that weren't visible in the last picture. I think it's safe to say that both of these pics are of Bert's Balance Beams.