The scratch marks around the screw are from L.T days when these machines were skillfully opened by tapping the screw round with a sharp punch.
I once had the pleasure of watching a retired Effra Rd Gibson mechanic open a couple of Gibson's this way in just a few moments.He said it took him 40 years to learn how to open a machine that fast.
He also mentioned that on the closing of the L.T ticket machine works in Brixton many Gibsons were just skipped.
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