This guitar is unusual due to the fact that the Type 510 pickup has been fitted independently of the bridge/tailpiece unit, and the volume/tone pots are also not fitted to the bridge/tailpiece plate.
Pot Code 278 indicates a date of 1968 (or 1958!)
Is this a Selmer UK Serial Number or a Van Wauw Netherlands number?
Comparison between this unusual Hofner Hawaiian (left) and the Hofner Hawaiian Standard Model (right).