Is it a Northfield? The Tidioute's are all steel if I'm not mistaken, including the bolsters. The Northfields are nickle-silver bolsters with brass liners.
Nickle-silver is brass, zinc and nickle. No steel.
I just tested my Barlow (a Tidioute) and the magnet sticks to the bolsters. The same magnet does not stick to the bolsters of my #15 Diamond Radio Jack (a Northfield).