NSBO pin

[Bhz64]

Please your opinions for this small NSBO pin.
The pin has a total length of 48.9mm, the NSBO badge has a diameter of 9.7mm and the weight is 0.95 grams.

Thank you in advance.

[DanCz]

Not a style or format i am familiar with - - i have a couple of early examples but neither look like this one. Other contributors may be more informative.

[Gaspare]

thats pretty rough.. Is the 'Black' paint or enamel? it the piece a low grade silver? or a pot metal?/silver washed zink? does it attract a magnet ?
Maybe this info will help another more familiar to ID its time period better [?]