Agreed the it appears to be early 1960s. It's definitely no older than 1961, assuming the calipers are OEM. The frame itself appears to be over dressed. The workmanship and stamped dropouts are typical for a mass produced frame of entry to lower mid-range grade, though the component mix would be considered mi-range for the era. As noted by John E it is probably hi-tensile steel and almost certainly not Columbus, with the best indicator of tubing grade being the seat post diameter.

Edit: If there is a serial number, it may allow us to identify the manufacturer.