There was a design change to the ‘Squire’ model that occurred late in 1966. The neck & headstock were kept the same but some changes were made to make the Squire “grow up” and be more like it’s more expensive counterparts – a logical improvement in the growth of the brand…..
A 3 way toggle switch was placed in the top lower corner of the pickguard ( and the guard reshaped accordingly ) rather than a slider switch down lower. This offered neck, or bridge, or both – rather than the Squire’s on / off bridge pickup.
The Mark 2 had separate volume / tone controls for each pickup ( therefore 4 knobs in all ) giving a whole new range of voincings to the instrument.
The tremelo was the same as the Squire one but a fully adjustable bridge ( as was used on the 12 strings ) was fitted.
( “ Mark 2” Photos courtesy of Mike Rizzotti )