01-31-2012, 09:22 PM
1) To control expansion with humidity. 
2) Philco knew that CA. would require earthquake straps for furnishings in the 21st century, and they wanted to get a jump on the requirement.
3) The radios were getting to heavy, the hole reduces weight.
If I had to take a wag, I would say that hot air was getting trapped at the top of the arch discoloring the finish, the hole provides a vent to let the hot air out. Even thought the back is open the arch support enclosed the top of it and hot air rises.
2) Philco knew that CA. would require earthquake straps for furnishings in the 21st century, and they wanted to get a jump on the requirement.
3) The radios were getting to heavy, the hole reduces weight.
If I had to take a wag, I would say that hot air was getting trapped at the top of the arch discoloring the finish, the hole provides a vent to let the hot air out. Even thought the back is open the arch support enclosed the top of it and hot air rises.
John
Las Vegas, NV USA
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
