Found it!
Its a Mico Electric Activated Brake Lock.
http://www.gmcmhphotos.com/photos/data/7009/medium/20170414_143413.jpg
I found info on it here:
http://bdub.net/gmcmotorhome.info/BRKLOCK.html
and here:
https://www.mico.com/sites/default/files/document-pdfs/81620016%20Brake%20Lock%20%28Electric%20Activated%29_0.pdf
https://www.mico.com/sites/default/files/document-pdfs/81620021Brake%20Lock_1.pdf
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Russell Keith
1978 Eleganza II
Dunedin, Florida
Its a Mico Electric Activated Brake Lock.
http://www.gmcmhphotos.com/photos/data/7009/medium/20170414_143413.jpg
I found info on it here:
http://bdub.net/gmcmotorhome.info/BRKLOCK.html
and here:
https://www.mico.com/sites/default/files/document-pdfs/81620016%20Brake%20Lock%20%28Electric%20Activated%29_0.pdf
https://www.mico.com/sites/default/files/document-pdfs/81620021Brake%20Lock_1.pdf
--
Russell Keith
1978 Eleganza II
Dunedin, Florida