An over-letter would not account for the sharp gap between the round bottom bulb of the "B" and the vestigial leg of the R, whereas a scratch and metal displacement would. All other proven B over R's or R over B's on other Victorian denominations show no such gap as metal flow on the die when corrections are made maintains smoothness. I'm not saying it's categorically not, but we need a much clearer picture to be certain either way. This is the best I can do with the original supplied image - I'm sure I can see a scratch...