[BC] processing way back when

[Barry Mishkind]

A discussion with someone has brought about the interesting question: 
what was the first audio compressor or limiter made for the broadcast 
industry?  That is, after manual gain riding of the 20s and 30s.

I'm talking about long before the Optimod, CRL or DAP.... Before the 
Max brothers.  Before the Collins 26U.

What was first used to stop stations from popping off the air on audio spikes?