This one is in via an anonymous reader. Based on the REAC label it appears to be a Reeves Electronic Analog Computer. Via Wikipedia:
"The Reeves Electronic Analog Computer (commonly shortened REAC) was a family of early analog computers produced in the United States by Reeves Instrument Corporation from the 1940s through the 1960s."
Followed by:
"There were seven models produced during the life of the system:
REAC 100 (1947)
REAC 200 (1952)
REAC 300 (1953)
REAC 400 (1956)
REAC 500 (1963)
REAC 550 (1964)
REAC 600 (1965)"
