If you google "THE SINGER CO. --- METRICS DIVISION BRIDGEPORT, CONN.", you'll find lots of information about that location. When Singer discontinued making sewing machines at this location in the mid-sixties, they continued manufacturing in the metrics division. I looked it up a couple of days ago, and if I remember correctly, they made some kind of scientific instruments. I'm not sure what this item might be, but may be a repairman's tool box.
bkay
Added:
https://microprecision.com/calibrati...b-fim-antenna/