Note the "Catshead" type bass tuners, as used on the 500/1 Violin Bass at that period.
Additional string length obtained by setting the muted bridge further back, compared to conventional Hofner solids.
A Hofner 188 (right) together with a Hofner 175 conventional guitar (left). The use of the same body, scratchplate, and electrics is apparent, as is the longer neck with a 30" scale on the 188.